This is a remix of a nice, modern style coaster holder I found on Printables. I needed to modify the original design to add spots for the rubber feet of my slate coasters to sit on.
The original model, which can be found here, was intended to hold square coasters that are up to 4" x 4" (101.6mm x 101.6mm). Although, the coasters I used in it were approximately 3.875" (98.4mm) square and were a somewhat tight fit. That might be because of the unevenness of the slate coasters I used. You might have to scale it up a little to fit your 4" coasters.
There are also matching coasters on the original model download page which can be found here. They were able to fit 6 of those coasters in this holder. I was only able to fit 4 of my slate coasters because to the added height from the rubber feet.
I printed these on my Prusa MK3S+ using a .4mm nozzle at .2mm layer height. I went with 25% gyroid infill to give them some extra weight and 4 perimeters to give them some extra strength. I didn't use supports, instead opting to slow down the dynamic overhang speed in Prusaslicer to 5mm/s for bridges. This worked great and I didn't have a single issue with the bridges. If your printer isn't great at bridging, you might need to enable supports. The top fill pattern I changed to octagram spiral for a bit different look.
The filament I used for these was Atomic Bronze Metallic PLA.
The author remixed this model.