Pretty lame isn’t it… just for adding stuff in the “Minecraft” section. Since they are just blocks, making different sized waterbombs make pretty nice generic blocks.
Large: One square sheet of uncut, square binder paper.
Mediums: One quarter the size of one square sheet of uncut binder paper.
Smalls: A square made from the strip of paper you get when you make a square out of binder paper.