We hear the term rolling the ball. In order to roll the ball you must putt thru it not at it. This requires a shorter back stroke and a longer forward stroke. Proper ball position is generally from center up to two inches in front of your belly button toward the hole. I don't subscribe to using the heel or instep of your forward foot to determine ball position because if you widen your stance for longer distances it throws everything off. The proper power source when judging distances is not how firm or how hard your putt stroke is. The width of the stance will determine the distance of the putt. Take the putter back to the big toe on your rear foot and releasing it through the big toe on your forward foot. Toe to toe. Now in order to release the putter head with proper acceleration through the ball so you roll the ball I use a drill. I place a ball marker about 4 inches in front of the ball. Focus on taking your putter over the ball marker then freeze and hold the putt until you hear the ball go in the hole. This will create the proper acceleration needed to begin rolling the ball in to the hole.