It's pretty easy to do, Pat. Just get 2 soft fire brick and rasp out a section on one side of each, then when you sandwich them together you have your hole for your knife. Drill a hole in the side of one brick just big enough to fit the tip of a propane or MAPP torch. I added another brick, which I sawed in half to cover the ends and hold more heat in. Wayne Coe sells the soft fire brick for $3 each, which is the cheapest I've found, and 3 of them can fit in a large flat rate box.