And by the way, LEDs do not necessarily need to light up, allthough that's their main purpose. But I'm not going to tell you crazy makers about hardware hacking... :)
Step 1: Preparation
Step 2: Cutting the sole
Step 3: Marking the zones
Step 4: Cut and place the LEDs
Step 5: Shape the shoe-topography
Step 7: Tape Strips
Step 8: Stick strips together
Step 9: Finishing the sandal
This action requires at least two hands and looks a bit awkward, so there's no picture of the process, sorry...
Now your geek sandal is ready, and you can start collecting LEDs for the other foot.