Every person slices a different amount and for different reasons. Some hit pull slices, some hit push slices and some hit top slices, but there are some common factors.
One, the club face is open…thus the slice.
Two, the hands are too active.
Three, the shoulders are not rotating properly.
Again, different combinations cause different amounts of slice, but there are a few universal things all slicers can do to REDUCE the amount of slice.
Better lower body rotation and less grip pressure will allow the club to release down the line better, which reduces slice. Better lower body rotation also reduces a hook, so you can see the merits of proper lower body. It’s very technical how this can be, but rest assured, more control in the lower body and less in the hands cures a lot of issues.
A tougher one that all might not understand…the more your left shoulder goes up on the downswing, the more the ball is likely to slice. You want your shoulders to turn more level. Again, that is a complicated concept and don’t try this unless you know exactly what I mean.