Run Wire and Install Old Work Electrical Box

What happens here

After drilling the hole, feed the Romex 12/2 wire through the newly created opening in the stud. Next, take an old work electrical box (distinguished by its side flaps) and insert it into the pre-cut hole in the mock-up wall. Secure the box by tightening the screws on its face, which will deploy and pull the side flaps tightly against the drywall or plywood from behind, holding the box firmly in place. Ensure the wire extends into the box. The video contrasts this with new work boxes, which have nails for attachment to studs before drywall.

Goal: Secure the electrical box and route the wire