Standing on one leg on a box, loop a powerband / superband around a fixed pole in front and around the back of your knee - just above the knee joint on the hamstring. Have the step box away enough from the anchor point to create a suitable level of tension on the band, ensuring you have correct alignment. Step backwards and downwards, bending at the hip and knee together. Don't let your knee roll in or opposite hip drop down. Focus on knee alignment keeping your knee cap on the outside of the big toe. Keep your front shin and spine all the same forward angle (30-40deg) and imagine sitting back down on a box. Let your back leg go backwards and shoulders come forwards. Drive through the heel of the stance leg to push yourself back up into the starting position and make sure yuo get your knee into full extension and squeeze the quads.

Make sure you down put weight through the back foot, or transfer weight into your toes when you straighten your knee