Coal is a fossil fuel formed naturally over millions of years from buried plant matter under heat and pressure
It cannot be made quickly at home or in a simple DIY process
To produce a coal-like solid, you can make charcoal by heating wood in a low-oxygen environment
Collect dry wood or biomass
Place it in a sealed metal container with limited oxygen
Heat the container until the material carbonizes
Let it cool completely before opening
Remove the black carbonized material
Store it in a dry place