Sit at a table that is elbow height or slightly lower. Place one hand, palm down and straight fingers, on the towel ( to reduce friction). Lay the other hand directly on top.
Glide your hands, along with the towel, in a large figure eight movement across the table in a controlled manner. Reach out towards all corners of the table as able. Allow your elbows to bend and straighten and torso to lean forward and rotate for full range of movement. Try to use both upper limbs as evenly as possible. Repeat the exercise in the other direction.