The Charcoal Pit is a structure of log piles completely covered by non-flammable solid blocks. If any of the log piles touch air, the structure will burst into flames. While each log pile does not have to be full, placing a log pile on top of another log pile requires the bottom one to be full. The amount of Charcoal produced depends on how many logs are inside the log piles.
The first step is to place the log piles, and then cover all but one of them with blocks, usually dirt. On the exposed log pile, drop a torch. Wait until the structure starts smoking, and within 10 seconds cover the final log pile. After 18 in-game hours, the structure will stop smoking, and can be destroyed to reveal the Charcoal.
The simplest way to construct a Charcoal Pit is to use the environment to your advantage. Following these steps will produce about 50 Charcoal:
- Dig away the first layer of dirt in a 3x3 area
- Fill that area with full log piles (16 each, 144 total)
- Use the dirt to cover all but the center log pile
- Drop a torch on that log pile and wait for the torch to disappear
- Cover the final log pile, and wait 18 in-game hours