Start with feet hip-width apart and parallel. Place the powerband over your outside shoulder and then under you foot and step down to generate the vertical load on the outside leg. Place the ball on the outside of the inside knee so it is snug against the wall. Don't lean into the ball, aim to and push your knee into ball to keep yourself upright. To perform the squat, make sure you move your hips backwards and let your knee bend - aim to bend at the hip and knee together. Don't let you knee roll in or opposite hip drop down, aim to keep both knees even. Focus on knee and hip alignment. You need to really think about sitting down backwards, keeping your chest upright, not just pushing your knee forward.

You will find it harder to push laterally into the ball with the inside leg so focus on this the most. If you don't have a swiss ball you can use a small pilates or kids ball, or even a pillow.