First, make sure that your instep, i.e. the upper surface of your foot from your ankle to your toes, are flat on your gound. If your toes instead of your instep are on the ground, i.e. if your sole is facing backward instead of upward, your opponent can easily dislocate your ankle by stepping on it.

Roll to your right side, with your right leg rolling accordingly. Thrust your left foot at the inner side of your opponent's right knee. A sharp thrust can dislocate his knee, so be careful if you do not wish to hurt him unnecessarily. A gentle push with your left foot on his knee and the momentum of your rolling over will cause your opponent to fall, enabling you to escape. The pattern you use is called "Carp Turns Body".