Four defenders move clockwise, each player always has a cone (or chair) to defend. When coach yells "shot", they box out, sit down with a low base, stay in stance for a couple of seconds.
To box out, locate your man, create contact, staying low, release and attack the ball, don't let the ball come to you, rebound above the rim. Make contact early, as the shot is being released, hit him with your hip and rear-end area. Don't run to where he is, run to where you think he is going (in this drill, probably halfway to a chair). If you make contact, he's probably going to stop and not even chase the rebound.