With your back flat, bend forward until your back is parallel to the ground, keeping weight in your heels and hips. (health.com)
With your feet parallel and toes forward, sit into a squat position with your body weight in your heels. (mindbodygreen.com)
Keeping your torso upright and weight in the heel of the grounded foot, slowly lower your body down until you feel a deep stretch in the hip flexor of the raised leg (b). (dailyburn.com)