With the twiggy fire method, you want heat below and above a pot or pan, creating a makeshift oven. You need a flat lid with no plastic parts, and yes, it will get black.
1) Use a stove (any type) turned down as low as possible. With liquid-fuel stoves, depressurize the bottle a bit to help reduce heat.
2) Place dough or batter (any recipe will do, or use pre-made dough) in a nonstick or greased pot. Don’t fill the pot more than halfway.
3) Build a small fire on the lid using twigs and small sticks; gather plenty to keep feeding the fire until baking is done. The size of the lid naturally limits the size of the fire.
4) Rotate the pot every five minutes to ensure even cooking. Resist the urge to check under the lid too frequently, which makes it hard to keep the fire going.
5) Wait about 20 minutes, depending on your recipe. When you can insert a pine needle into your baked goods and it comes out clean, you’re done.
(Note: Only use this method when fires are permitted and safe.)