You can try to keep your right elbow bent until after you hit the ball, flipping is caused by an early release, usually due to extending the right arm which pushes the hands away from the body. Pretty hard to flip the wrist without the right arm straightening. This also keeps the left arm extended, if one bends the other tends to extend. Since we want the left to control the arc, it must be the extended arm at impact, so if you have trouble doing that, work on the bent arm is sometimes easier to do. Both arms do extend, but it is well after the ball is gone, centrifuge force will take care of that....