1. Dig the fire chamber. Excavate a pit 1 foot in diameter and 1 foot deep. Now widen the base of the chamber a few inches so it has a juglike shape. This lets you burn larger pieces of wood.2. Dig the air tunnel. Start a foot away from the edge of the chamber, on the upwind side, and carve out a molelike tunnel 5 or 6 inches in diameter, angling down toward the base of the fire chamber.3. Build your fire in the chamber and top the hole with a grate or green saplings stout enough to hold a p...