No crazy wire forms or cabochon needed! All I used was a flat bottle cap, a power drill (to make a hole for the split ring,) a leather chain, E6000 glue, and a fabric flower.
Step 1: Start the Locket
(Sorry no photos for this step.) You want to start by gluing down your fabric flower, or whatever adornment you're using, to the front side of the bottle cap.
Then, you want to take your photo sleeve and cut out two circles each large enough to cover one side of the bottle cap. (You'll be gluing one circle to the front and one to the back.)
Step 2: Drill a Hole for the Split Ring
If your bottle cap doesn't already have a hole in it, this is when you want to drill one. (Pictured are the front and back sides.)
Note: This can require quite a bit of force and a couple of minutes depending on what your bottle cap is made of.
Step 3: Finish the Locket
Hang it on a chain of your choosing and you're done!