This is a great series of stretches for your hamstring, groin, and outer hip.
Use a resistance band or long towel to help assist your leg.
First, wrap the resistance band around the bottom of your shoe and hold onto the other end of it. Start by bringing your leg straight up towards the ceiling. Keep your leg as straight as possible. You should also focus on driving your opposite leg into the ground, to create separation between the two.
You’ll stretch your hamstrings by pointing your toes up to the ceiling and then bringing them back down toward you.
Next, bring your leg out and to the side to stretch your adductor/groin.
Finally, bring your leg across your body to stretch your tensor fasciae latae – the muscle on the outside of your hip. Remember to keep that leg as straight as possible!
You can also turn this stretch into an ab exercise by holding one leg up in the air as you actively bring the opposite/unsupported leg up and down.