This base securely holds the square reader and makes it just a little easier to operate.   The two halves slide into place neatly securing the reader, and allowing access to the power button and charge point.

The orientation is reversable.

I have allowed for two M3 inserts in the base and two M3 screws, however one would be perfectly adequate and at least while it's new the fit should be a nice firm slide, as a worst case a bit of tape over the bottom seam would easily secure the two!

PRINTING

I've oriented the parts on their sides which will give simple support free printing.  Depending on how neat you want them to look, you can make the layer height as thin or as thick as you like - the versions pictured were prototypes printed at 0.25 layer height, but if you don't mind spending another hour waiting for a flawless print, .15 should result in a flawless finish.