Keeping the cut straight, cut the leather strap in half.
Wrap one end over one side of the crystal opal square, and mark a spot to punch a hole. (Total loop size will be about 1"). Remove from crystal, and use a small binder clip to keep the leather folded evenly. Punch a 2mm hole (the smallest size on our rotary leather hole punch) through both layers at once.
Wrap around the crystal, and from the back side, push the longer part of the rivet through both layers, then top with a rivet cap.
Set back of rivet on a steel block or anvil, and place curved side of rivet setter over rivet cap. Tap rivet setter firmly with brass hammer. (If the rivet is still loose, try again harder.)
Repeat for other side of crystal.
Before adding clasp, check size:
For an average woman's wrist, fold over about 1/2", punch hole, and rivet onto one size of clasp. Make a simple loop at the other end, with 1/2 - 3/4" leather (make sure you can pull it onto -- and off of! -- the Z clasp before punching).
For a small wrist, fold over 3/4" or more for these final loops.
For a larger wrist, you can either use 2 strips of leather (cutting each to the desired length, or finish the ends with gunmetal straps tips, a lobster clasp, and a few large gunmetal jump rings to make it the correct length, and to hook the clasp into. Adding a few extra jump rings, even makes it adjustable length!
1 each #04-439-30-30 Swarovski 4439 Square Link, 30mm - White Opal