Adafruit gives out aluminum coasters with large orders. They're very nice, but they stick to the condensation on the bottom of a cold glass. This grille breaks up the coaster's top surface so your glass won't stick.
I modeled this in Fusion 360. I've included the .f3d file and .STEP file, so start with one of those if you want to redesign it. Please do redesign it; my pattern is okay, but I know you could come up with something better.
I've printed this in PLA, PETG, ASA, and ABS. They all work fine. The model is optimized for 0.2mm layer height. I used the default 2 perimeters and 15% grid infill; I'm sure other values would work too.
The author marked this model as their own original creation.