In this clip Grand Master Pierre Laquerre (9th dan) shows one of the static stretching exercises he uses for the hip flexors.
This stretch is great for the iliopsoas muscle group, or the muscles collectively known as the hip flexors.
In the position shown, push the rear back back as far as possible, or until you feel the stretch at the front of the hip. Then turn inward for an added stretch and hold for 20 to 30 seconds.
See this and many other stretches Grand Master Laquerre teaches in this video.
This free clip is a sample of the Taekwon-Do Stretching video by Grand Master Pierre Laquerre