Wait to cut the excess ribbon until later.
While planning your design, put on the shoes and see where they bend when you walk. Space your ribbon so as to avoid placing the LEDs directly where the shoe bends. The connections between the soft ribbon and the hard LED epoxy blob are the most fragile part of the ribbon, and repeatedly flexing these connections may break the circuit.
If your ribbon must span a flexing area, avoid applying glue to the span, so the ribbon isn't forced to bend as sharply as the shoe.
Pull the needle through the plastic loop on the battery pack, and pull the thread most of the way through.
Separate the doubled thread and pull the needle between them, then pull the thread taut. Now the thread is looped securely around the battery pack!
Remove the double-stick tape one section at a time, getting ready to glue.
Use tiny strips of painter's tape to clamp the ribbon to the shoe while the glue dries.