A slice is a golf shot that initially begins on the left of the target and then curves to the right, finishing off target to the right. It is caused by swinging the club head across the target line through impact.
To explain this, place an alignment pole on the floor. The pole represents the target line. The far side of the pole is the outside and the side that you are standing on is the inside. A slice sees the club head approaching the golf ball from the far side of the target line and then being pulled into the golf ball and across the target line to the inside to hit the ball. As you are making this action with the club head, known as its swing path, during your swing, the club face is aiming to the right of the swing path, but left of the target. The aim of the club face is 85% responsible for the flight of the golf ball and because this is left of the target, the ball starts left of the target.
However, because there is a difference between the club face aim and the club head's direction of travel, this imparts tilted axis spin on the ball and the ball curves to the right. If there is a big difference between the club’s swing path and face aim at impact, you will see a big curve during the ball’s flight and it will finish off target to the right.
To improve a slice, you need to work on swinging the club head straighter along the target line, with the club face aiming at the target. Try this drill to achieve straighter golf shots. Take six golf balls and create a swing channel. Take two of the balls and place them one inch to the left of the ball you are going to hit. Place one ball two inches outside the target line and the other two inches inside the line. Take two more balls and place them one inch to the left of the ball you are going to hit, one ball two inches outside the line and the other two inches inside the line. Place the final two balls outside and inside the target line. Initially, swing your golf club through the channel without striking any of the six golf balls.
Do this slowly at first and then gradually build the speed into your swing and then finally actually strike a shot from the channel without hitting any of the other six golf balls. Work on keeping the club face aiming at the target as you swing the club head through the channel and you will correct your slice and begin hitting straight shots.
Another really good drill to work on achieving to cure your slice is to swing your golf club and keep your forearms really close together as you hit the ball and follow through. This will force you to rotate your body through the shot and to rotate your forearms, closing the club face so that it aims towards the target. As you make this action of keeping your forearms close together, point your forearms out towards the target after you have struck the golf ball and you will begin hitting straighter golf shots.
The third way that you can improve your slice and hit straighter shots is to place an alignment pole, or use your stand bag, on the left of you (if you are a right handed golfer). Place the pole into the ground on the target line two feet towards the target and lean it at a 45 degree angle on the inside of the line. Work on swinging the club head just over the pole, rather than under it and keep the club face aiming at the target as you strike the ball and then rotate the face down towards the pole as you swing over it. Do this slowly and without the golf ball initially and gradually build your speed back up and then re-introduce hitting the golf ball.
All three of these drills will get you hitting much straighter golf shots and you will see your accuracy really improve the next time you are out on the golf course.