My epoxy hot box is quite simple - just a simple frame of rigid foam insulation screwed together with LONG screws. (The front cover is not shown in the picture below.) There is absolutely no strength in this structure but that's fine because I don't move it around and it bears no weight. I installled one light bulb as a heat source for now - later this will be two bulbs and a thermostat. Currently I must monitor the temperature of the box and make sure it doesn't get too hot - I just only turn on the bulb an hour before I plan to use it.
You must be VERY safety-conscious if you follow in my footsteps. The aluminum foil is conductive, so the light bulb is actually mounted to a junction box that contains the wiring, and there are no sharp edges for wires to catch on. Don't let it get too hot, either. This type of insulation is flammable if exposed to flame or extensive heat (somewhat more than wood). Finally, note that one side is more reflective than the other (a stamping on the board indicates which) and should face INTO the box.
I have a very accurate digital scale for measuring my epoxy, and I plan to work by weight rather than by volume. I purchased the set of cheap-o West Systems epoxy pumps (I am using MGS 335) with the intention of doing as other builders had done and keeping the epoxy in Hefty gallon-size freezer containers (see Jeff Wilson's site, et. al.). However, I could not find suitable containers, and in the end discovered that the pumps fit the MGS bottles just fine if you don't mind the resin pump not actually screwing on. I also intended to work by volume and make the modifications to the pumps' depth controls discussed by others, but discovered that measuring by weight is so much easier (and more accurate) that it's not worth the effort and risk (of making a mistake).
Larry Wimble has created an excellent spreadsheet for MGS 335 that shows you precisely how much of each component to mix for a desired target quantity. I have cached a copy here in case he (re)moves the file - it's only 6K. Hope you don't mine, Larry
Building this project required:
1. One sheet of 1-7/8 rigid foam insulation ($23.25)
2. One junction box ($1.25)
3. One box-mount light bulb socket ($1.06)
4. Cut-off cord from a trash-bound device ($0)
5. Screws and masking tape ($0.75)
6. Four (for future replacements) 40W light bulbs ($.96)