im no expert at it, and I don't have a vac machine, but basically have a block with the part on top having the parts edges around 1/4-1/2inch off the base if youre just doing a couple pulls. if its more of a long term thing that youll do multiple runs youre gonna want to make a buck, you can do this by doing the same thing but an inch above the base and use clay to fill in the area around the wood, making a mountain to prevent lockup and to ease the plastic around the piece which will minimize any folding or webbing. mando armor is very low in shape so you wont need to worry about it whereas a helmet would web up and have all kinds of crimps around the edges. after that you can make a rubber jacket mold, and fiberglass mothermold on top of that, then after the clay and armor are pulled out, fill the mold you just made with plaster of paris or any other heat resistant material to make your buck. plaster absorbs the heat after multiple runs and eventually will be prone to breaking down or cracking, which is why most bucks are constantly needing to be patched up.
or yknow, that's the general idea from what I understand.
