If your stance consistently aims to the left, for example, you’ll naturally find a way to push the ball to keep it on target. Instead, lay a club on the ground to help yourself consistently set up correctly to your target.
Slices are caused when the clubface stays open (angled outward) through impact, which puts sidespin on the ball. Often, beginners have a weak grip, which leaves the clubface open at impact. Instead, using a stronger grip helps you get the clubface square through the ball.
To strengthen your grip, if you’re right-handed, turn your left hand over so you can see more knuckles. As you swing through the ball, a strong grip will help you keep the clubface closed (facing straight down the fairway) compared to your swing path, which will help you eliminate the slice and get more draws.
The swing plane is an imaginary two-dimensional plane that follows the line that your club shaft makes (when looking from behind the ball). Often, beginners have a swing plane that’s too flat — when viewed from the side, their club shaft is far too horizontal (or like swinging a baseball bat). As they go through impact, they lack the strength and skill to close the clubface and they send the ball curving on a slice.
Instead, make sure the club is on the correct swing path. Practice swinging the club as you would a baseball bat, then progressively lower the swing until you’re in a more vertical/upright position
If you have a chronic slice, you might have an outside-in swing path: while in the takeaway, instead of drawing the clubhead straight back, it drifts slightly up and away from the body forcing you to pull it back in during the downswing, resulting in a side spin.
The fix: On the takeaway, imagine drawing the clubhead straight back and don’t allow your elbows to flare out. On the downswing, avoid “chopping” at the ball and keep your elbows slightly tucked in.
If nothing else works, it could be your equipment. Many beginners don’t have the clubhead speed to necessitate a clubshaft with normal (or higher) stiffness — this could potentially cause your clubface to always be open at impact.
If this is the case, go to a golf equipment store and take a few swings in the testing area to determine your clubhead speed. Based on this data, they can give you a recommendation for best clubshaft for your swing.