One of my favorite drills for perfecting the impact position is to do what is known as the “clap your hands” drill.
What this drill does is help you get a sense of what it means to stack your left side at impact and make solid contact into the golf ball.

To get started, address the ball as you normally would, only don’t use a club this time. From here, go ahead and simulate a big backswing, but when you do it, keep your left arm in the same position from start to finish, which should be pointing at the golf ball.

Finish the simulated backswing, then on the forward swing, let your right arm come down and through and actually clap your left hand.

When this happens, your body should be situated just as shown in the photo, with your left arm stacked over your left leg, the hips open and the shoulders square to the target.

If you practice this drill often enough, you’ll not only ingrain the proper impact sensation, but also prevent your shoulders from spinning out of position and taking your eyes off the strike with the ball.