Chapter 3X - Education
Chapter 3 is full of information about the materials used in construction, the methods for using them, quality and inspection criteria, etc. The end of the chapter has several practice pieces that teaches the builder various techniques that will be needed in the upcoming chapters creating actual flight hardware.
I have called this 'Chapter 3X' as I didn't do everything as shown in the plans, and instead did other things not shown. I covered all of the same techniques and more, however. I certainly learned a great deal.

I live a long way from the nearest Aircraft Spruce warehouse. 11,261km in fact. Thus, the cost of shipping materials is a significant portion of the total materials cost!
For economy reasons, orders to be shipped half-way around the world are best in few large orders, rather than many smaller ones.
For my first practice layups, and having never used the materials before, I didn't want to make a large order for materials in case I decided I didn't like working with composites after all.
I purchased a small 'epoxy repair kit', then I contacted a local composites shop and asked if they had any scraps they would be willing to part with. Perhaps because it was right before Christmas they kindly donated me a few cuts of different cloths and a few different pieces of foam. I later discovered that the bi-directional cloth 'sample' they gave me was 7725, exactly the stuff specified in the plans!

My first trial layup was 6 plies of BID in a rectangle about 8" x 4". I wet it out then put a piece of clear plastic wrap over it and rolled it (with a small table leg that I had nearby!). It came out nicely, a few epoxy wrinkles where there were wrinkles in the plastic, but generally it worked well.

Then I microed a small piece of foam onto a small square layup (that had cured earlier), microed the edges to form a fillet, then laid up a few more layers on top. My first sandwich piece certainly inspired confidence in the strength of this structure!
About this time I crashed my EPS foam RC plane. Dragging a wingtip during a high-speed pass is bad! It pivoted around and sheared the nose off ahead of the wing. Luckily, none of the expensive bits were damaged, and with the high-mounted engine, there was no damage there, either. Just shattered foam where the battery and actuators reside in the nose. I can fix this!

I microed two pieces of urethane together and microed them to the rest of the foam airframe. I then carved the foam to a 'pleasing shape' that was a bit different to the original shape (that would have been boring, right? Let the mods begin!).
I followed this with 2 plies of BID overall, lapping onto the original EPS foam fuselage.
After cure, I cut a 'canopy' for access to the inside, and a cooling vent forward of that (similar to the original). I carved out enough of the foam inside to make space to glue in the actuators and provide battery space in the nose. I did not replace the steel weights in the tip of the nose, figuring the glass over foam would be a bit heavier anyway (not much, as it turns out). I even glued in the original plastic canopy clips, enabling the canopy to clip on and pop-off like the original.

After verifying control travel, I took it for a test-flight. Success!
A spray of primer then orange paint, and it looks like it was always that way!

So that's carving foam and laying up over a complex shape, educated!
When I bought my motorcycle (a '97 Suzuki RF900), it had a baggage pod attached. Attached to a pack-rack with rusted wire and a cracked wooden board. That didn't stay on for long; it wasn't about to come off by itself, but I cannot operate with that sort of workmanship on my ride (there was no duct-tape or anything!).
After fixing the RC plane (not for the last time), I was inspired to create a fibreglass mount for the baggage pod. How hard could that be? I would create something with a panel that the pod mounts to, with two sides that taper down to a lower cross-member that would pass under the seat in place of the grab rail, and bolt down to the same points as the grab-rail.

Using the scraps of PVC foam I had previously 'aquired', I created the top panel (using the 'hinge method' to join small pieces together), sides and crossmember / attachment. Then i glassed them separately. The top and sides worked fine, but my attempt to wrap the glass around the tight radius of the crossmember edges didn't work quite as well. Well enough?
I then glassed the parts together with 'tapes' (really scraps and cut-offs from my dwindling supply of BID). I imbedded large area washers to the points where the pod bolted to the front of the top panel (the aft was a slotted piece of metal that the pod clipped to). I didn't use bushings or a solid core. Yes, I crushed foam when bolting it onto the bike!

It worked, mostly. Because the top panel was attached aft of the crossmember, the flex of the mount caused the pod to bounce up and down, enough to hit the after fairing. Not good. I stuck a piece of soft foam in between, in the interim. 
That was version 1!

After a few months of use, the pod was in no danger of coming off, but the excessive flexing had initiated cracks where the crossmember met the sides. The crossmember itself had some delaminations, too. Time to modify.

I bought some 200GSM BID from a local supplier, and created a new crossmember. This time I laid up several plies flat (I forget how many), set a piece of MDF in the middle as the core (with the sides tapered down) then laid up more plies on top, creating a glass-to-glass bond along the long edges (see, I'm learning). After cure, it was clear this was FAR stronger than the last one.
In an effort to reduce the flexing at the join to the sides, which had to be fairly small to fit into the gap between the fairing and the seat, I sprayed expanding foam (not the good stuff) at the join after floxing the crossmember to the sides, carving to a smooth taper. I then glassed over the join.
I created a 90deg angle of glass (6 plies?) using a wooden form covered in plastic wrap. I cut this in two, and glassed onto the after underside of the top panel to create flanges to mount a support strut at the rear. The fairing at this point had a centre-panel behind the seat and between the fairing sides. I created a glass replacement using the original as a mold. I then cut a hole in the middle of it (didn't want to destroy the original, see?) for the strut to go through. Also lo-vacced these parts using a matress inflator (not much pressure, but worked in principle).
The strut was a length of PVC foam, rounded on one side and glassed overall. A U-shape of glass (formed exactly the same as the strut, but with the foam removed) was then floxed onto the end, and the join glassed. This U fit over a cross-wise steel tube under the fairing, and I bolted through both to create a strong, removable connection. The strut was bolted to the 90deg flanges under the top plate. 
By now I had long exhausted the epoxy repair kit, and was using a small kit of West. Learned about exotherm about this time, too...
The result was a strong, stiff structure with almost no flex.  That was version 2!

This worked well for a few months, until I noted more flexing developing. That's weird...
When I had a free day, I removed the assembly, and found to my shock that one of the two bolts between the strut and steel tube was missing (learning about lock nuts or safety-wiring?), and the other was still there, but had torn through the glass, probably due to insufficient strength in the glass in that area once the other bolt was gone, doubling the load and introducing some twisting.

There were possible options for strengthening the strut attachments, but I decided to attack it a different way. I cut off the sides, preserving the crossmember and top panel. The top panel glass had been a mix of fabrics, and was a bit rough around the edges, so I revised the shape slightly (trimmed bits off that were not really needed) and glassed on a ply or two of the 200GSM BID. The crossmember was fine, but I removed the spray-foam tapers.
I built new sides, eliminating most of the overhang to the rear, and made them taller to ensure I could still fit the seat on underneath. This meant the rear seat was occupied by the pod when fitted, but I vary rarely used the rear seat anyway. This would would almost eliminate the twisting load that had caused so much flexing before. Glassed the sides separately again.
I added PVC foam and micro to radius the inside corners to ensure the glass would conform nicely, then read the chapter in the plans where the winglets are attached to the wings.
By now I had received an order of the plans BID and UNI from Aircraft Spruce, and decided to use the UNI to wrap from the crossmember bolt-throughs, up the sides (on both sides) and onto the top panel. I beleive I used 6 or 8 plies on both the inside and outside and peel-plied.
The resulting structure was by far the strongest and stiffest so far, as you might expect! It barely budged with a 10l bucket of paint placed in the pod.
At this stage I microed the surface and sanded to a roughly smooth surface. And sanded and SANDED and wow this is much harder that I expected!! I didn't do another layer of micro to perfect the surface, it was 'good enough' for this application. I then primed and painted it black, to match the fairings on the bike.

The third and final version of the glass pod-mount worked perfectly, and I sold it with the bike about a year later (the new owner could not have been happier). It was light and strong, and most importantly had taught me a lot about the materials and processes involved in this composite contruction method. I did have to helicoil one of the bolt-holes in the bike structure after having the pod and grab rail off and on so many times!
The difficulty in sanding the micro surprised me, but I was willing to move forward with that in mind. Which I guess is a testimony to my commitment to this project, as I later discovered that what I had bought and was using was not pure micro at all, but a micro BLEND. You know what it's blended with? Fumed silica. The stuff you add to epoxy to make it cure really HARD and TOUGH. What an oaf!

Before finally moving on to aircraft parts, I bought 20l of a new (to me) epoxy I intended to build with. ADR-246TG it's called, and it equals or exceeds the specifications of the plans approved epoxies, none of which are easily obtained in this country (except West, with which I had a little experience with by now. That experience -exotherms very easily when warm, even in fairly small batches, and relatively high viscocity- and being the lowest spec of the approved epoxies made me want to use something higher spec).
One possible drawback of the ADR-246 is that it requires post-cure to 50deg to develop full strength. I will carry this out with larger assemblies (ie tub, wing, strakes, nose, etc). This temperature is still well-below the 75deg limit of the wing foam.
I built the plans 'confidence piece' using my final epoxy and the plans BID and UNI. It worked out fine, and is as strong as is claimed.