If you're negligent about teaching how to catch a fly ball in the sun (or to slide properly, for that matter), and your players get hurt, lawsuits can occur. When a player gets injured, the first question inevitably asked is: was he taught how to do this properly?
To teach this technique properly, line up the kids facing the sun and have them drop one foot back to get a sideways perspective on the ball; this way the ball comes out of the sun more quickly because of the angle. Simultaneously have them shield the sun with their glove. Look to see if a shadow is cast across the face. Next, drill the outfielders by lining them up and short-tossing pop-ups, just as you did in the sliding-catch drill.
Excerpt from Ch. 7, pg. 153