Set up and Key Actions
Standing at the top of your mat in tadasana, come into a "half chair" or "gentleman's chair" pose by flexing your right foot, crossing your right ankle over your left thigh, and sitting your hips back evenly like you would for chair pose. If you find your right hip is pulling forward of your left, draw the right outer hip back so that it's level with the left one. Bring your fingertips to the floor (or blocks) in front of you. Keep your right foot (especially the pinky-toe side) flexed, and keep your hips level. Engage your low belly.
Plant your hands on the floor and start to shift your weight forward a little, bending your elbows, bringing your right shin against your upper arms (as high up as you can), wrapping the top of your right foot around your left upper arm, and coming onto the ball of your left foot. Round your low back, but move your chest forward as you shift forward. As your weight shifts forward, you may be able to squeeze your left heel in toward your seat. From here, you may be able to extend your left leg back and up. Draw the left side of your belly toward the right side of your belly to keep your pelvis from rolling open toward the left as you lift your leg. Gaze slightly forward—like you would for crow pose.
If lifting your left foot off of the floor and squeezing your heel in toward your seat has you stumped, you may find it helpful to practice with the ball of your left foot on a block. Even if your foot doesn't hover just yet, this extra lift will help you get a sense of what the pose feels like when it's airborne.