This stretches both the hip flexor and the quad at the same time. It's a pretty advanced stretch, so if this is too difficult, stretch your quads doing this standing quad stretch instead. Or if this is too easy, do this kneeling hip flexor stretch against a wall.
From Low Crescent Lunge, bend your right knee and use your right hand to pull the right foot in toward your right hip, holding the top of the foot with your right hand.
Rest your left forearm on your left thigh. Or for a more advanced version, hold the right foot with the left hand and twist your torso to the left, resting your right elbow on the floor next to your left foot.
After three to four minutes release and come into a Low Crescent Lunge on the left side. Perform that stretch and this kneeling quad stretch, holding each for three to four minutes.