I never used the so-called sock stop or latex before so here are the istructions on how to use sock stop or latex:
1. Cut out the areas you want to paint with latex from cardboard. This is simple when you made the slippers for yourself: You just draw the shape of your feet on the cardboard (doesn't have too precise) and cut it out.
3. Put the cut-outs into the slippers, turn them around and paint the pattern on the back.
Be sure to use a paper or something similar to protect the surface you're working on from the latex.
4. Leave it to dry for about 24 hours so you can be entirely sure it's dry. Voilà!