Nine-Sided (Enneagonal) Box
A fairly easy modular by Dennis Walker. Enneagonal since it has 9 angles, but it’s actually a nonagon which stands for 9 sides.
It holds together all right since all the modules are solidly interlocked.
Paper to use
I used thicker paper to make it, but I think normal paper would be better. You need 9 square papers to do it, 3 of each color.