Dynamic hamstring to hip flexor stretch on the spot (Hamstring dynamic stretch, high kicks to opposite hand/swinging leg back, with heel lift)

Stand up straight with a wall to your side.
Swing your affected leg up in front of you.
Keep this elevated leg straight as you rise up onto the ball of your stance foot.
Reach your opposite arm forward, aiming to kick your foot to your hand.
Swing this elevated leg down and back, allowing your knee to bend and your foot to swing behind you.
Your stance foot will flatten on the floor.
Reach your opposite arm up towards the ceiling as you do this.
Repeat this movement.