A coaster that is designed so that multiple can be stacked on each other. The pattern on the bottom will slot into the pattern on the top.

I have had issues with this model, as the corners have curled every time I try to print it. This may be due to my printer not having good cooling, or that I was using wood PLA. I will continue to adjust the tolerances and print with different materials to see if I can get a better quality print.