The quickest thing I could think of was to melt some metal within a chamber of bricks. These aren’t even firebricks! I surrounded the chamber with dirt to help insulate it. The white pieces inside the chamber are some flat marble slabs I found.
Here is just a look at the “dirt furnace” from behind.
In this pic you can see the crucible inside with the burner in position. Now I need to add the remaining bricks and some more dirt.
Here the burner is sending ripping heat into the chamber. At first the burner was sputtering and hesitating like it was about to cut off. I had the burner to far into the chamber and simply pulling it out some solved the problem. It works best with the tip of the flare just barely inside the chamber.
It's really blazing now.
Here we get a little peek into the hot chamber. The aluminum is molten in the crucible. It took about 20 to 25 minutes with this poorly insulated setup (heat and steam escaping all through the loose, porous soil). In a real furnace I think it’d be molten in about 10 to 15.
Here's a look at the hot crucible still in the chamber. There's about 1 1/2 pounds of aluminum in the crucible.
Here is the furnace after the carnage. Still hot of course, even though it doesn't look like it..