Coaster with a japanese wave pattern loosely based on the idea from https://www.thingiverse.com/thing:4823069

Put a color change in at 2.00 and 3.80 to use different colors. If you use Octogram Spiral as the top and bottom fill pattern you have a nice pattern on the bottom. I uploaded the PrusaSlicer File for more information.

When changing the openscad file reduce the $fn value to something like 10 to ensure faster processing time. Increase it again before exporting it to a stl. If you want bigger waves change the waveWidth Parameter in the OpenSCAD file.