This posture is good for stretching hamstrings, releasing the back, calming the nerves and improving sleep. Don’t do it if you have high blood pressure.
Bring one hip close to a tree or a wall
Swivel the legs up the support, and lie on the ground. Keep the feet active. Push through the heels and spread the toes. To stretch all three hamstring muscles, you must make sure your legs are straight (at least part of the time). Straighten the knees by drawing your femurs towards the tree, but don’t strain the hamstrings. If need be, move further away from the tree.
You can do this with or without a block under your sacrum. The sacrum should be evenly pressing into the support to build stability and a strong foundation in your sacral area.