Place a 5 gallon bucket in front of the pitchers mound and have the pitcher, working from the stretch, set his front leg on top of the bucket, simulating the position of the start of his leg kick. Make sure the pitchers front leg is not too far out in front of his body, otherwise he will not be balanced. With proper upper body in set position, have the pitcher hip load (lift front leg off of bucket), and stride towards the plate, pitching the ball. The back leg should follow through and touch, or knock over the bucket.
This is a great drill to teach young pitchers the proper leg kick and upper body positioning required for pitching.