Step up against the wall 1 leg at the time. Hands shoulder wide apart. Keep your elbows locked and scapula elevated. Look at your hands at all times.
Push your hips away from the wall slightly so they end up on top of the hands and shoulders. Do not allow your shoulders to move towards the front during this push out.
Stay close to the wall. Nothing moves but the working leg. Slide it up against the wall and extend the knee.
Bring the second leg up to join the first one. Keep your scapula elevated and core engaged. Nothing touches the wall but the feet. Look at your hands.