One of the causes of hitting the ball on the bottom of the club is that you might have too much lateral movement while you swing. As you set up you might move too far behind the ball, get stuck behind the ball, and actually hit the ball on the upswing, thereby catching the ball on the bottom of the club. Or you might make a good backswing but as you come down you move too far in front of the ball to where you can’t reach the bottom of the ball, once again catching the ball on the bottom of the club. The secret to fixing both of those problems is to reduce the lateral movement both ways. Try to get a sensation of being more centered over the ball. A good exercise to help you to do that is to set up with your feet together. This reduces your ability to shift too much from side to side. So put your feet together and practice clipping balls off the tee, keeping your feet together. You can see from my swing that I did not have that much lateral movement; I was able to stay centered over the ball, thereby getting solid contact rather than catching the ball with the bottom of the club.