When people slice the ball it really means that the clubhead is coming out to in and often it gets very very steep as well so the angle and attack of the ball isn’t shallow enough.
So one way to promote a shallower angle of attack hitting more from the inside to get rid of that slice would be to practice making swings almost with ball above the feet or even practice swings almost like a baseball style.
So, you can hit shots with balls above your feet. That will actually just make the swing a little bit more rounded. See how it’s a little bit flatter as well. Be very very difficult to come right over the top of it if the ball is above your feet.
Maybe if your just warming up and you’re on the tee. What I would try and do is just make sure that you start by swinging the club in a very level manner trying to keep the clubhead level.
It doesn’t want to change it’s angle at all. If you practice swinging round once you start getting the posture in, then the swing is basically that. It will go up and down on a similar plane but something that’s flatter than you’re used too.
So if your not hitting shots just practice swinging the club around your body in a baseball fashion.
If your going to hit shots doing this. Just have the ball maybe one foot above you I suppose. So it just promotes that flatter plane swing and a more inside approach that’s much shallower and you’ll see some better ball flights.