Summarize the following:
Choose one that is high enough to let your legs hang freely over the edge. Your thighs should be supported by the table, and your legs should be bent at the knee. Clasp it with both hands. You can grab around the leg, under the knee. Alternatively, you can grab behind the thigh. If you can't get all the way to your chest, it's fine. Keep it there for 30 seconds. You should feel a stretch in the front of your pelvis on the leg that is hanging down. That muscle is your hip flexor, which contributes to slouching and back pain with excessive sitting.

Summary:
Lay down on a bed or bench. Bring your right leg up. Pull your knee towards your chest. Repeat 2 times on both sides.