I've also been contemplating on the fact that I'm not the only busy person out there, and plenty of folks seem to do a fair amount of hobbying despite adult-life commitments. I've been wondering if hobbies, like most pursuits, exist in a feedback loop, and that maybe I can keep the hobby interest up by dabbling in a small amount of constant exposure instead of focusing on large but infrequent events. To that end, I've been making terrain for 10mm games and thought I'd share a bit here.
OK, on to the topic of the post. Since I plan to play some games at the smaller scales, I've been making terrain with thin bases. Listening to wargaming podcasts and reading blogs, it seems a common complaint are terrain bases, especially thin ones, that warp. The picture above shows one of my very thin bases, free of warping.
Tools required are scissors, a Sharpee or similar alcohol marker, spreading utensils (I use disposable cutlery from the office kitchen), and a spray-bottle or similar method of adding controlled amounts of water. Masking tape, push-pins, or staples help for step four below.
Step one: cut your plastic into the desired shape for the terrain footprint, making sure it's big enough for whatever trees or buildings or whatnot you plan to mount on it. I find an old pair of normal stationary scissors cuts through thin PETE packaging just fine.
Step two: rough-up the surface of one side of each plastic base with some 60-grit sandpaper, giving it enough tooth for the fiberglass tape and putty that comes later.
Step three: use the Sharpee to write some sort of key marker on the base, like a number or letter with an arrow associated with one edge.
Repeat steps one through three for as many terrain pieces required.

Step six: cut out each terrain shape from the wax paper, cutting the fibreglass tape along with it. Ensure you cut 1 mm to 2 mm inside the marker outline, so as to create a slightly smaller shape than the original plastic base. You have now essentially created peel-off fiberglass tape stickers corresponding to each of your plastic bases.
Step eight: mix up a small amount of putty, sufficient for one terrain base. Roughly estimate the amount of wood glue required to completely coat your terrain piece in a thin (~0.5 mm) layer, add this to your mixing container to start. Sprinkle in the Durham's, mixing until the consistency goes from honey (i.e. the wood glue alone), to a thick, chalky peanut-butter like texture. Next, add small amounts of water until the honey-like consistency returns. You should be able to pour the mixture but just barely.
Step ten: decorate each base as desired.
I could just cut thin MDF pieces like everyone else but I enjoy this method for the ease of decorating noted above, as well as the ability to use simple scissors to cut complex terrain footprints.