Keeping your putter low to the ground is crucial when holing out. To do this I concentrate on my setup and posture and pay attention to keeping my hands high so the putter sits flat on the ground.
That helps keep the putter low – if you arch your wrists or lock them you will put in some wrist hinge on the way back.
This gets me in a great balanced position; my eyes are over the ball, my elbow positions similar and so the forearms are level. Having everything parallel is the best way to keep the putter low to the ground.