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. You contact the ball at 4 o'clock not the back of the ball (3 o'clock). Aiming for the back of the ball leads to trying to guide the club head down the target line and even worse leads to coming from the outside the target line and actually hitting the ball at 2 o'clock.
Hit 'em straight!