Standing a few feet from the hole, set up to the ball as you would a regular putt. Instead of taking the putter back, limit your stroke to just the follow-through motion. You are basically just “pushing” or “rolling” the ball to the hole. This forces you to accelerate into your follow through.
There are additional benefits to this drill. You will notice that the ball has more forward roll, which keeps it on line much better. This drill also encourages the left wrist to remain firm instead of breaking down. You will not only enjoy keeping the ball on a better line, but notice improved distance control as well.