If you feel pain in the knee, support the knee or back off from the stretch.
Start with your knees bent, feet on the ground with your heels in line with your sitting bones. Thread the left foot through the triangle of the right leg and bring your left knee down to the ground. Use a support under the knee (egg or brick) if taking the knee to the ground makes the sacrum uneven on the ground.
Place your right ankle on your left thigh, outside of your left knee. Flex both feet. Note that both thighs are evenly extended from the midline of the body, so your legs form a balanced “Y” with your torso. The shinbones should be stacked on top of each other.
Lift the bottom of the belly and extend the thighbones away from the body, slowly rotating the legs away from the hips. In the full pose, the left knee is on the floor and the right ankle is on the left knee.
Hold for 3 to 9 breaths, then change sides.
If, when you do full pose, the upper leg is higher than a 45° angle from the ground, do the following variation instead:
Start with your knees bent, feet on the ground with your heels in line with your sitting bones. Cross the right ankle outside of the left knee.
Use a strap to lasso the right ankle; bring the strap up towards your shoulder and hold it like a ski pole, with the back of your hand towards the ceiling and your thumb towards your head.
Straighten your left leg on the ground, keeping the right ankle just above the left knee as you extend the left leg. Slide your hand on the strap so it rests on your left hipbone (ASIS).
Keep your feet active with toes flexed. Keep the left leg active, quads contracted with all the toes pointed to the ceiling and the foot flexed.
Take your right hand to your right thigh and use it to externally rotate your right thigh and traction it away from the socket. Lift the bottom of the belly. Move your right knee away from your left hipbone and your left hipbone away from your right knee.
Hold for 3 to 9 breaths. Repeat on the left leg.