I've written about this before, but do *not* attempt to build one of these unless you know how to safely empty a propane tank and get the valve off ot it. Just don't. Anyway, beginning with an empty, de-valved tank, you start by using ViseGrips to break the welds holding the base in place. You have to wrench pretty hard back and forth to weaken the welds till they snap, but there are only 3 or 4 of them.
