Old, fond memories from childhood – drawing with spirograph tools*.

Coasters. Buy them in pairs or in pack of six. The latter includes a cardboard box to store them in – also made and assembled by hand by MFY.
 
As an example, the color bronze is shown here, but they are of course available in all of MFY's colours.
 
*) Spirograph is a geometric drawing device that produces mathematical roulette curves of the variety technically known as hypotrochoids and epitrochoids. [Source: Wikipedia]

CARE: Suitable for any kind of glass/cup. When with hot beverages in ceramic or glass cups, the coasters withstand up to 80°C. Hand wash.