Making charcoal traditionally, in a dirt mount

You can obviously scale this down. If you use clay instead of dirt, you need to poke vent holes in them and block/unblock them accordingly to control the burn rate. They are usually situated at the bottom.

Some people build a chimney in the center, either by planting a few posts and leaving a gap inside them or by stacking wood in a cross hatched fashion, building the chimney up.

I suspect that letting the fire burn down to the bottom offers a slower burn which is preferable.