kreative said:
continental and remember to follow through, don't chop
I do not recommend a pure continental for the forehand slice, I will move it more towards the Eastern forehand grip. The Eastern forehand grips helps stabilize the forearm movement and to maintain a firm wrist.
In order to develop a good forehand slice, practice freezing the racquet swing when you make contact with the ball. The swing path should come from a higher position from the incoming ball and then flatten out as it makes contact.
You do not want to hit the ball with force, just let the racquet drop in the groove and glance the ball. Freeze and balance yourself on your front foot. Hold it for 5 seconds. By doing this you will learn how to time the ball, balance yourself in the shot. You will also learn what racquet face angle you need and will learn what wrist position, swing path, etc, you need to produce a certain slice.
I usually aim for the top half of the ball just above the balls center in order to not "CUP" the ball underneath which floats it long. If you are off balance the arm usually compensates and the racquet face turns or your wrist turns the entire racquet right before contact. This produces numerous errors.
The main thing about the forehand slice is, it is not a "forced" anything. Just glide the racquet into the ball. All you have to do is focus on racquet path and racquet face angle.
Use gravity from the somewhat low to high swing to provide the right amount of power.