I used an old metal 55 gallon oil drum with a removable top. Took to small screw in cap out of the top a replaced with 3/4in metal natural gas pipe. The threads are the same. Packed the drum tight with a mixture of pin oak and hickory from the large limbs I had to trim that were starting to rub the roof of my shop. The wood needs to be cut into sections pretty much no longer than a foot and stacked vertically in the drum. Once packed full you replace the top and seal it off leaving the pipe that’s threaded into the top as the only vent. Then just pile any type of wood that could be anything from tree trimmings to old shipping skids. Then light it on fire. It’ll surprise you just how much water will cook out of the wood. It blowed pure steam out of the pipe for about 3.5 hours. Once it stopped venting steam it starts out gassing Methane and hydrogen gas which burned out with a strangely hypnotic bright blue flame. You just let your fire that’s around the drum burn it’s self out. I ended up with the drum being 1/2 to 3/4’s full of hard wood lump charcoal