You need 8 wooden planks to craft a chest.
- Chests hold the same amount of space for items as in your inventory, since the hotbar is not actually extra space in a inventory.
- It is not possible to place most blocks directly over a chest and have it work. There must be at least one block of free space above the chest to allow it to open. Some blocks work, though, like stairs, halfslabs and other chests.