The old zipper action is copping a flogging at chateau Cuppa & Cake. The cubes are deliciously comfortable, filled with the very affordable but deadly bean bag balls.
When making cubes filled with bean bag balls, make an additional cube out of scrap, place it inside the flashy cube and fill the insert with balls. Then cut the flappy zippy thing off on BOTH ZIPS. If you wish to re-open the cube later, then use a paperclip to thread through the zipper head. REMEMBER, bean bag balls are unsafe for our littlest elf's.
If you want to have a go at your own cube, I used a 43cm square template and I am more than happy with the size.