A good swing starts with a well balanced and solid set up
Many slicers hit the ball to the right simply because they are lined up to the right, when they go to hit the ball their mind knows the target is to the left and then subconsciously changes the swing to outside in so that the club travels towards the target causing a slice
There should be a slight weight shift in the swing, very minimal going back to your right side on to the inside of your right leg followed by a subtle bump to your left side on the initiation of the downswing getting the weight forward and eliminating fat shots