When talking about a golf swing, the slot is an imaginary box that you look into as you address and hit the golf ball. The sides of the box are defined by the distance between your feet, and the golf ball lies on the outer line of the box. To understand the importance of dropping your shoulder in the slot, imagine swinging a golf club while standing erect, instead of bent forward at the waist. In this position, it would be impossible to swing the club on the correct inside-out plane. On the other hand, bending too far forward causes you to swing the club on an erratic plane. Dropping your shoulder correctly in the slot is essential to your swing.
Select a club that you hit with relative consistency. Address the golf ball in your normal stance and visualize the sides of the slot that extend outward from the inside edges of your feet.
Start your backswing and stop when the club is parallel with the ground. At this point, your head has not moved and your front shoulder, that is the shoulder toward the target, has started to drop in the slot.
Continue your backswing and hold when you get to the top. Visualize a line from the top of your front shoulder to the golf ball. If the line is not exactly vertical, rotate your hips more and drop your front shoulder until the line is vertical. Take note of your hip rotation in this position.
Address the ball in your normal stance. Start your backswing with the intention of rotating your hips and dropping your shoulder in the slot to achieve the vertical line to the golf ball. Take your normal swing and lift your shoulder out of the slot as you follow through.
Continue to practice hitting the ball and dropping your shoulder in the slot. Hit several shots using a wood and learn to drop your shoulder correctly in the slot while swinging longer clubs. Practice pitching and chipping and learn to drop your shoulder correctly in the slot when hitting shorter clubs.