When golfers come to us struggling with a big slice, they very typically have a pretty weak top-hand grip, which allows the clubface to stay open throughout the swing. We also see a tendency for these players create too much of a forward ball position, which promotes more of an out-to-in swing shape. When you combine a weak top-hand grip and a forward ball position, that’s how you get your big slice.
The first thing you want to do to fix this issue is to strengthen that top-hand grip by rotating the hand away from the target so that we can see at least three knuckles on our lead hand at address. From there, move your ball position a touch further back to promote more of an in-to-out shape and more of a draw shot.