Step 4: Variations
Cat food cans are not the only cans you can use, but beware of deeper containers, to get parts out you need to reach in with your fingers. If the container is narrow and deep you can not get your fingers down there. Picking the unit up and turning it over is not usually the best way to find a part as you dump out all the cans.
I layered out the containers for close packing, you may want a more rectangular arrangement. This leave more space between the containers for parts to get lost in. The space could be filled up with some paper mache to prevent this.