This pose helps you let your back and hips relax.
Lie on your back and make of your legs a stable four-sided pyramid. Your knees are the top. Your butt is at the base of a side, and your feet are at the corners of the opposite and wider side. Your upper and lower legs form the edges of the pyramid.
Get on your back on the mat. Bring your knees up and put the soles of your feet flat on the mat so that your legs form a stable triangle. Let your knees drop together and rest on each other. Then move your feet apart slightly so that your legs are also stable side to side. This lets your groin relax. Reach into your groin and touch your adductors, on one side or both, and feel the difference as you let your knees fall together. Let your touch guide you in how you place your knees and feet.
The base of the pyramid is not a square. Place your feet wider than your hips, but be comfortable and don’t strain to go wide. The pose works by being relaxed and comfortable. In yoga poses that look like this, we put our heels roughly finger tip distance away from our shoulders. Try different positions of your feet.
Then lift your butt slightly, just off the mat, and tilt your pelvis back, tucking your tailbone in and pushing your pubic bone up, as we do in many yoga poses. Then put your butt back on the mat with your pelvis tilted. And relax; your pelvis will move a little as you relax. This pelvic tilt helps your lower back relax.
Lift your head just off the mat and extend your arms toward your feet and extend your head away from your butt. Then rest your head back down and relax. Use a pillow if you want.
Put your arms anywhere you find comfortable. Your fingertips resting lightly at the top of your groin can help your awareness of tension you are holding and help you to allow your deep hip flexors to relax.
Press your lower back (lumbar) against the mat. Hold the press for some seconds then relax slowly. Then do the press again.
Friction holds your feet in place and you just relax into the pose.
Stay in the pose for a while. Minutes. Ten minutes. Twenty minutes. Set a timer on your phone so you ignore time and just relax. Slowly your hip flexors will let go and relax.
I’ve taught this as part of yoga for a couple of years. I like it better as a last pose because corpse pose is uncomfortable in the lower back for many people. And I like it as a reclined “home” pose for people that are tight when we work on opening and releasing their shoulders and hips.
Putting your knees together and your feet wider makes your thighs rotate inward (medial rotation). That doesn’t work well for some people.
You can use constructive rest from Alexander Technique, from which this pose derives. It has your knees raised and legs parallel, which doesn’t relax your groin (adductors). And you may need effort to hold that position.
Or you can do the position bound. I use wide ribbon as it is comfortable, easy to find, and affordable. Cut and tie a loop of ribbon that fits loosely around both your thighs near your knees. Slide the loop of ribbon on your legs before you do the pose. Then slide the ribbon on your thighs toward your pelvis when you do the pose. The ribbon supports your thighs and helps your groin relax.
“Muscle Synergies of the Hip and Pelvis” by Sian Smale