Lie on your back with your legs extended. Your partner should be kneeling beside you. Raise one leg up towards the ceiling and have your partner hold the ankle. Your partner can use their shoulder to brace your leg if necessary. This will be your starting position.
With your partner holding your leg in place, attempt to flex the knee, contracting the hamstrings for 10-20 seconds.
Then relax your leg, allowing your partner to gently push the leg towards your head. Be sure to inform your helper when the stretch is adequate to prevent injury or overstretching. Switch sides once complete.