Creating an INSERT for use as a DM decal template (Patreon)

A recent user asked how to create a square INSERT template for use with Decal Machine. His goal was to create a bunch of these different INSERTS and then lay them out like some sort of control panel, then create different DM Decals based on the collection of them.

This only focusses on the creation of the initial INSERT, not the DM Decal.