This is probably kind of obvious but you want to plant and begin your slide before you make contact with the ball, that is you want to slide just enough to get your racquet comfortably to the contact zone and no further. That way there are no extraneous movements further past the ball than needed and you can recover/focus on the next shot.
Another thing which might help is to time the movement of your feet to where you generally (not 100% of the time) make that last step and plant with your RIGHT (that is, the back foot on the forehand) that way you can plant your foot further back if you need the space to properly make contact. Hope that makes sense. Good luck!