Setting Up
Push a standard box formation toward the ball side, and start both post players outside the zone's two wing defenders rather than in their usual spots. Neither post should face the direction he's about to screen — giving that away early is the easiest way to lose the advantage.
The Chained Screens
The first post sprints up and sets a screen directly on the top wing defender. The instant that screen lands, the second post runs off his teammate's back and sets his own screen on the bottom wing defender — one screen leading straight into the next.
The Corner Cut
The shooter watches for the first screen to land, then sprints off the second screener's back to the corner, ready to shoot the moment he arrives. The inbounder delivers the pass for the three.
Coaching Points
If the top defender ducks under the first screen to jam the shooter's path, have the shooter go over the top of it instead and still get to the corner.
If both wing defenders fight over the top of their screens, use the weak-side player as a safety valve, and teach both screeners to slip and show themselves to the inbounder if that happens.
Neither screener should square up toward his assignment before the play starts — that's the single easiest way to give this away.