Let’s borrow from Alexander Technique.
And I make a few modifications I find beneficial.
Get on your back on the floor and bring your knees up.
In yoga poses that look like this, we put our heels roughly finger tip distance away from our shoulders. Try different positions of your heels.
Let your knees drop together and rest on each other. Then move your feet apart slightly so that this is stable. This lets your adductors relax. Reach into your groin and touch your adductors, on one side or both, and feel the difference as you do this. Let your touch guide how you place your knees and feet.
Then lift your butt slightly, just off the floor, 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 floor with your pelvis tilted. And relax; your pelvis with move a little as you relax. This pelvic tilt helps your lower back relax.
Last, lift your head just off the floor and extend your arms toward your feet and extend your head away from your butt. Then rest your head back down and relax.
Put your arms anywhere you find comfortable.
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 and just relax. Slowly your hip flexors will let go and relax.
This pose goes really well with Happy Baby pose and Warrior 1.