Dry your feet completely, if they are wet. Put on a pair of dry socks that reach past your ankles to keep them from falling into the shoe.
Place your big toe into the corner of a plastic grocery bag. Pull the bag firmly over the rest of your toes, the bottom of your foot and heel.
Pull an ankle sock over the bag. The ankle sock holds the bag in place without worry that it will slide down the leg.
Trim the bag back so that it doesn't hang out over your shoe. The exact length to which you trim it depends upon your preferences. Leave more plastic back then you intend to use, then trim until comfortable.
