Get it right going back
One of the biggest backswing mistakes I see is when a player rotates the lead arm over the trail arm right away. That makes the club pull to the inside, putting it immediately out of position.
To feel the right movement, pick up a range bucket that’s half full of balls and get into your setup. Simulate your backswing, keeping the bucket aligned so the balls stay in (far left). Only when you get to the top should you feel the bucket turning so that the balls fall out – right as you start down (left). That’s the position you want to be in to fire into impact.
To fix a slice, don’t dump the balls on the backswing.