Drag your fingertips along the surface of the water during the recovery (the part of the stroke where you hand moves from your waist to where your hand enters the water. Some coaches include the entry in the recovery. Others include the entry as part of the catch. I just talk about the entry as a separate entity and say that there’s 4 parts to the stroke instead of 3). Shoulders must roll a sufficient amount for this drill to feel normal. If you swim flat in the water you’ll get “bound up” as you try to drag your fingertips forward.