I have never taught a predominant slicer that did not always have their clubpath travelling from out to in on a very consistent basis. I have never taught a predominant hooker that did not always have their clubpath travelling from in to out on a very consistent basis. In order to upgrade these golfers' ball flight we needed to improve their path first and then work to adjust the face to point somewhere between the path and the target line.
Here is an example of a lesson I might give to a golfer who predominantly fades/slices the golf ball:
I hope these two clips help you to better understand what it is you need to do to improve your ball flight and have more fun out on the golf course.