These printable designs are foldable versions of your favorite regular 3D shapes, the five Platonic Solids! The shapes are flat (in the form of the polyhedron's net), but when printed in a flexible filament, they can be folded up into the finished shape.
Print in a flexible material such as NinjaFlex, Cheetah, or WillowFlex.
In the YouTube video I made on the subject, I have a section that is a tutorial on how to design your own. The same process can be applied to making any convex solid shape. I've also included the .123dx file so my existing designs can be downloaded.