This drill uses props that are always near at tennis court, chairs, specifically practice the proper recovery movement and positioning required for singles on the baseline.
Set up two chairs about 2 feet behind the baseline and 3 feet on either side of the center hash mark. A partner, coach or a ball machine can give balls to the player who is on the chair side of the net. These are wide and after hitting the ground strokes, the player recovers to sit in the correct recovery chair, specifically the chair diagonally opposite from where the player hits the ball.
The player will quickly learn that when they hit cross-court, the recovery distance to the correct chair is less and much easier.