Step 1: All you will need
2) a washer (a couple times larger than the hole and flat as possible)
The purpose of this instructable is to get the fastest, easiest way to get back in commission.
Step 2: Half way to getting your step back
Peal back the bottom layer and run both ends of the string through the hole and rap around the flip-flop strap and back down through the hole again and tie it to the washer.
Step 3: Jack is back
(side notes) it may help to burn the knot if you used a nylon cord. and any kind of adhesive between the layers could only help.