I just took a golf lesson (my first in ten years of playing) the other day. I have a slice as well.
Here are the corrections I received:
1. Rotate my grip counterclockwise over the handle so that my index and middle knuckles are visible from above and the “v” on my right hand is on top.
2. Narrow my stance so that my feet are under my shoulders.
3. When addressing the ball, align the butt of your club with your zipper.
4. When swinging and just prior to contact, you want the trajectory of your club head moving in to out instead of
out to in (which creates the slice). My pro had me stand “straight” but hit 30 or so degrees to the right to get the “in to out” motion.
5. After contact, you want
to rotate your club face counterclockwise so that it faces behind you more or less by the time it reaches knee or thigh height.
The overall effect is to hit a draw by making contact on an inside to outside trajectory and rotating the club face counterclockwise during the swing. The clubface movement should naturally align with your right forearm if your grip is right.