Thanks for all of these incoming tips guys! I am benefiting greatly from your experience.. I managed to get the belt loops onto the bag, so it's officially a belt bag now.
As I think forward to attaching the deer (hair-on) piece to the leather, I'm also working out the mechanics in my mind. I initially thought that I'd sew the two pieces together, and THEN attach the final piece to the bag. But that would mean that the stitch row that will go along the top of the flap that gets sewn to the back of the bag would have to go through both the leather and the deer, and with the fur, that's a non-starter.
Instead, I think I'll sew the two pieced together EXCEPT for across the top, then sew the leather piece of the flap to the back of the bag, and THEN one last stitch across the top to join the deer with the leather.
Does that make sense?