Lie face down on the ground, with your arms to the sides and the elbows bent, so that your arms form a big W-shape.
Activate your Abs and get into a posterior Pelvic tilt .
Lift your arms off the ground by activating your upper back muscles ( Shoulder retraction ) and hold them up for time.
Form tips
You will be tempted to arch the back, and engage the lower back muscles. Do not do that! That would shift the focus away from the scapulas and completely change the exercise. Instead, focus on keeping the Abs engaged, and pull your bellybutton up towards your spine. The back should be flat, and there should be a space between your belly and the ground.