Below is a graphic that I use when teaching my students. Along with Ben Hogan's secret I have my students think of themselves addressing the ball from standing at the 6 o'clock position facing 12. The target would be at 9 o'clock. The goal is to swing the clubhead from 4 o'clock to 10. The body rotation will square the clubface at impact. I also tell them that they want to contact the ball at the 4 o'clock position which would be the inside quarter of the ball. I am sure this visual will help you eliminate your slice and lead to purer contact.
Hit 'em straight!