Lay the collar flat and mark two more spots at one-inch increments on either side of the center mark.
Use a ruler to mark the top-bottom center line on the collar as well.
Pierce your NeoPixels through the collar with the flat sides all facing the same way (away from where the GEMMA will go).
Use small pieces of wire to make a continuous power bus, and do the same with ground.
Pierce these marked spots with the awl. Prepare three pieces of wire by stripping one end, then thread them through the holes in the leather.
Use a piece of Velcro tape to affix the battery to the collar right next to the GEMMA. We arranged GEMMA and the battery so the collar slack covers/protects them. The battery wire wraps around the collar once, then plugs into GEMMA. This is how you turn the collar off/on.