A simple drink coaster that provides simple entertainment at the table, and can be customized with engraving or laser etching. Carve two halves from provided SVG file and glue together. Center pocket can be milled out for weight reduction, and minimizing the effects of bowed stock material. Mill magnet pockets to depth of 0.5 mm more than 1/2 the diameter of the magnets you are using (they need a little wiggle room).
You will need…
Wood sheets, 1/4″ or less, but at least 1/8″ thick.
Spherical magnets, 3/16″ or ~5 mm.
See this project in action: