Have you noticed that if you try to hit the ball really far it usually finds trouble? This is because trying to crush the ball often means a big lateral lower-body slide toward the target. The body races ahead of the ball and the hands can't catch up in time to square the clubface. It's either open, resulting in a slice, or closed, producing a hook.
The pivotal part of this lateral slide is made by the left foot. Usually it spins up onto the toe as the club comes into impact. This may be done in an effort to rotate the hips, but instead it causes the hips to slide laterally. If you've ever struggled with a reverse weight-shift, spinning with the left foot may be a result of your effort to make sure you get over to your right side.
Whatever the reason, your hips must move in harmony with your arms and the club; if the left foot has spun onto the toe, the hips are ahead of the game. To counter this tendency, focus on keeping the left foot flat on the ground coming through and just past impact. Anchoring the left foot prevents the left hip from making a big lateral move, giving your hands and arms time to square the clubface. Once impact is made, the foot rolls onto the inside of the sole, then onto the toe for the final position.
Practice swinging the club with the left foot anchored on the downswing, both with and without a ball. But keeping the left foot flat doesn't mean keeping your weight on the left side. Your weight should transfer as it always does. If it doesn't, you'll create a new series of problems.
DRILL: PLANT BOTH FEET
Try hitting your driver without allowing either foot to lift throughout the swing. Focus instead on slightly rolling your feet to the left on the backswing and starting the change of direction to the downswing with a little roll to the right.
At no point should your heels lift off the ground. Keeping both feet planted will give you an exaggerated feeling for what it's like to slow down the hips and allow the hands and arms to catch up.
