The most common cause of a slice is an out-to-in club path with an open face at impact. The drill that I like to have students use to work in this is a drill involving the use of an alignment stick and a swim noodle. Take the alignment stick and push it into the ground on the same angle as the club’s shaft angle when addressed that you are hitting. Place the swim noodle over the top of the alignment stick to prevent any chance of injury if the player still swings out-to-in while doing the drill. Place the ball directly behind the alignment stick and have the player try to hit the ball without hitting the stick. This drill will help promote a more in-to-out path.