Firstly, make sure your body alignment is correct, your shoulders, chest hips and feet should all be parallel to each other as well as parallel to the ball to pin line. If your body is not aligned correctly and is aiming too far to the left, the upper body can not and does not rotate properly. This leads to an ‘out to in’ swing which means that the club will not be hitting through the ball but instead will be moving from outside the ball to inside the ball as the impact takes place. The consequence of this is side spin being generated on the ball and the dreaded uncontrollable slice follows.
Even if your alignment, swing and grip are perfect, the positioning of the ball in the stance can make a good straight shot into a shot that slices wildly out of play. This occurs when the ball is placed too far forward in the stance.
Once again the slicing of the ball occurs because the club face is no longer square on at impact with the ball. This is because the club face has come past square and is moving in from the ball to pin line, this again generates side spin resulting in the ball slicing again.
Ideal ball placement is different for every club, but this is a rough guide:
For woods and long irons, the ball should be placed inline with the inside of your left heel (opposite for left hand players), for short irons place the ball in the centre of the stance, for medium irons the ball should be placed between two positions mentioned above.
Posture should be checked as weight distribution can also have an affect. Having your weight too far forward can encourage the slice so be wary of your weight distribution.
If all else fails, try strengthening your grip. Do this by moving your hands slightly clockwise around the club, then adjust your grip so you’re holding it more in your fingers and lighten the pressure, this should help reduce the affect of the slicing.