Begin on all fours, with your knees directly below your hips, and your hands slightly ahead of your shoulders. Slide your right knee forward to the back of your right wrist; at the same time angle your right shin under your torso and bring your right foot to the front of your left knee. The outside of your right shin will now rest on the floor. Slowly slide your left leg back, straightening the knee and descending the front of the thigh to the floor. Lower the outside of your right buttock to the floor. Position the right heel just in front of the left hip.
The right knee can angle slightly to the right, outside the line of the hip. Look back at your left leg. It should extend straight out of the hip (and not be angled off to the left), and rotated slightly inwardly, so its midline presses against the floor. Exhale and lay your torso down on the inner right thigh for a few breaths. Stretch your arms forward.
Then slide your hands back toward the front shin and push your fingertips firmly to the floor. Lift your torso away from the thigh. Lengthen the lower back by pressing your tailbone down and forward; at the same time, and lift your pubis toward the navel. Roll your left hip point toward the right heel, and lengthen the left front groin.
If you can maintain the upright position of your pelvis without the support of your hands on the floor, bring your hands to the top rim of your pelvis. Push heavily down. Against this pressure, lift the lower rim of your rib cage. The back ribs should lift a little faster than the front. Without shortening the back of your neck, drop your head back. To lift your chest, push the top of your sternum (at the manubrium) straight up toward the ceiling.
Stay in this position for a minute. Then, with your hands back on the floor, carefully slide the left knee forward, then exhale and lift up and back into Adho Mukha Svanasana (Downward Facing Dog Pose). Take a few breaths, drop the knees to all-fours on another exhalation, and repeat with the legs reversed for the same length of time.