The sling-back dilemma: solved!

Feeling brave today, ladies? (Male readers: this will be of no interest to you whatsoever. Just go away until tomorrow and I'll put something normal up.)
Here's how you can solve that miserable situation of the too-loose slingback. Whenever I wear a sling back, the strap is far too large although the rest of the shoe fits. If that's your problem too, here's an easy fix. And you get to play cobbler!
You need:
Sewing supplies - a thimble, thread (preferably upholstery), needle, seam ripper, and scissors
Glue: either Shoe Goo or a similar epoxy
So. Start with adorable shoes

Got these at Buffalo Exchange for free after trade!

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Get really brave. Feel along the strap to where the elastic stops. Cut the strap.

Use seam ripper and scissors to remove piece of strap from elastic. You can cut the end of the elastic into a point.

Trim some of the strap if needed. Use the seam ripper to help open up the strap, like so.

Spread the insides with glue, insert elastic, close tightly, and clamp with a clothespin or your fingers for several minutes. Let dry.

Starting to sew...

 To reinforce, sew around edges. Be very careful and use a thimble - needles are hard to push through tough leather or its fake, cheap cousin. After tying off the thread, smear the area on the back with a little more glue to make sure the thread ends are secure.

Ugly smeary back

 I didn't do a fantastic job here, and the glue shows. But seriously, who could see that from a standing height? Except two year olds, who don't care anyway?

Those aren't cankles! It's just the angle, I swear!

Repeat with the other shoe.
Hints: fabric straps and cheaper shoes are easier to work with and you can even use a sewing machine.
Hide your thread ends on the back. You can be a little messy - but get some good, strong stitches in - on the back of the strap.