I made these slippers from scratch, but you could definitely mod some slippers and skip most of the sewing.
Step 1: Materials
-2 coin cell batteries
-2 coin cell battery holders
-2 slide switches
-fleece, furry material anything you want to make the slippers out of.
-sugru to make treads(optional)
Step 2: Make pattern and cut out pieces
For the top of the slippers, I used the technique they used in the this instructable. Cut out two tops from the fleece and two from the fur is at least two inches longer than the fleece. This will be folded over and your LEDs will be inserted.
Step 3: Put together circuit
Solder together your circuit in a compact way using a soldering iron and make sure everything is well insulated so there is no chance of a short.