There are 3 main things that cause a ball to fly a certain direction: 1) Where the club face is pointed at impact, 2) Which direction the club is swinging at impact (inside-out, straight, outside-in), and 3) Contact (toe, centre, heel). To stop slicing, we have to first get the club face more closed. From there, we need to learn to swing more inside-out. Both of these things need to happen to have the ball flying straighter. Then understanding that where you make contact on the face is massively important. With the driver specifically, a ball hit off of the toe will impart hook spin. Vice versa with a heel strike, imparting slice spin.