Foldable Ruler (Credit Card Size)

Supports: No
Infill: 20 - 50%
Walls: 4
Layer Height: .2mm
Nozzle: .4 or .6 ( works best on .4mm nozzle)
 

Print-in-place design.  Move the arms around a bit to loosen the joints at first. No supports are needed.  I used a blurring tool to clean up the edges so everything closed properly.  The first layer with the bed might stick out a bit and need clean up.

If you want to do multiple colors you can do a filament change at Layer 15 and back to the original color at layer 19.