Hot Glue Gun
Again, originally I had planned on these two pieces remaining separate, but since it was just going to slide over the leg, I attached it all together (this decision really simplified things, a lot!).
In this step I added an elastic strap that would go underneath to shoe. This elastic served two purposes: to hold the boot down on the shoe, and to make it more oval instead of circular.
I then hot glued the heck out of everything. Here is the completed results.