I had to go to a birthday party and as typical for me, decided that a hand-made gift would be more valuable. I got the idea from a different type of interlocking coasters I had seen a while ago. I drafted the 2D drawing in OnShape. The coasters were cut and engraved from 5mm thick birch plywood, on a Universal Systems laser cutter (not sure which model).
Cutting in progress:
Here are some more pix:
