Low-Straight-Push

The proper bowing effect of the hands and wrists combine into a feeling of downward extension at impact. This is essential for solid ball striking. This is true for a chip, pitch, punch or full swing. At the core is the ability to delay the hands as long as possible. And when the hands become active they unload in a de-lofting fashion. Think about how the club face "opens" away from the target when the swing starts. The club must "close" in order to be square at impact. But simply closing the club face, by itself, does not accomplish the proper angle of attack into impact. Loft must be reduced resulting in the club head remaining low after impact.

The unloading act leading into impact has the effect of compressing the hands, especially the right palm as it braces for impact. A reasonably proper grip places the palm of the right hand more on top of the handle and the pressure is downward keeping the hands relatively low through impact.

TEST IT

While holding a club with a generally good grip take the set up and simply apply more pressure with the pad of the right thumb. Don't swing it. Simply apply the pressure. The toe of the club will naturally move a little left and the hands will press forward, de-lofting the club. 

Zach Johnson

If you are going to have a fault, be ahead of it and de-loft the club. The ball will launch low. De-lofting the club requires the opposite action of flipping the hands, typical of the average golfer. Learn to de-loft the club head regardless of where the body's overall weight is. It is very difficult to hit a ball hard and low when the weight is too far back or away from the target. Maybe even impossible. I find most students can resolve this fact by reacting to the feedback from each shot. The pattern of the ball flight's trajectory will represent the success. Don't sneak onto your back foot and try and add loft. That process is counter to solid ball striking. While practicing this approach I would expect a lower ball flight that is either perfectly strait or a low strait push shot.

Below are two related posts and the original Golf Digest article featuring Zach Johnson.

Punch It
Anchor The Turn
Zach Johnson How To Get Back To The Ball