A slice is all due to a faulty connection to the handle. What I mean is putting hands on the Handel in a position that causes the clubface to be open at impact. The number one drill that came out of a test on lots of people on how to cure a slice , came from the people being tested. They said of all the things you teachers said to do, turning the toe of the club inward at address was the best cure and quickest cure.
A “strong grip” with both hands placed on the right side of the Handel, exaggerated, then moderated if needed is best for the long term “swing for life!”