Only two things control the direction of the golf ball - the direction the club is facing and the direction the club is traveling. If the club is traveling towards the target and the club is facing towards the target the ball will fly toward the target.
Most people have the ability to swing their arms toward the intended target so the trick is to get the club to face in the same direction. A simple homemade training aid will help you do this.
Take one of your golf clubs and tape a ping pong paddle to the shaft of the club so that the paddle and the club face are pointed in the same direction. Now swing the club toward the target while watching the face of the paddle. Normal coordination will allow you to control where the paddle faces. If you have the ability to use a screwdriver you can do it.
Practice doing this without a golf ball until you learn how to do it and get comfortable with it. As you get used to how it feels you are learning to do it without thinking about it. The more you practice it the faster it will become automatic.
A final note about slicing. A slice is caused when the face it pointing right of the directions your arms are swing. Nothing else. When you get the face (or the paddle) to face in the direction of the swing the ball will go straight in that direction. Since most slicers swing from out to in this means you will pull the ball straight left until you fix the direction of your arms.
If you don’t have a ping pong paddle the next best thing is a tennis racket. Grip it with both hands and swing it like a golf club.