Initial experiments. Began with a stack of cinderblocks. Bottom one had a corner broken out, lit a fire there. Put fuel in through the chimney at first, got it going fairly well. Decent updraft but not a lot of heat. Added cement blocks around the base, this allowed the fire to come out of the bottom of the chimney. The updraft in the chimney did pull on the flames a bit and the pot o water got quite hot. I tightened up the blocks and that improved the draft. Kept shoveling fuel in but never got to boil.