To use, start a fire and the put something like a iron trap door over the top of it and then simply throw your item above the fire on the trap door and wait for it to cook

- This can only be used to cook one item at a time per block (because when there is multiple items together they stack and then can't be cooked)

- it is much slower than a furnace and you have to manually watch cook every item

- And in general it is much worse than just using a furnace so it is only really useful for cooking a small amount of items when you don't have fuel for a furnace and it adds a bit of
immersion which is always nice.