Train your aim
A key component to holing putts inside 10ft is accuracy in the ball’s starting direction. With just one degree of start line error hitting the edge of the hole on a straight 10ft putt; training your aim to become laser-like buys you some stroke error allowance.
If a player were to aim 0.5 degrees left on a straight 10ft putt; then deliver 0.5 degrees of closing in stroke (between set up and impact) they’ve missed the putt. Tighten up that face aim to under 0.5 of a degree and you’ve made the putt with the same stroke.
When using your Visio template or Putting mirror be sure to match the face perfectly to the face aim line. Leaving a small gap at the back of the putter face (so you can see a gap between the leading edge of the face and the face line on the training aid) can make it easier to register if it’s sitting square or not. Whereas sitting the face close to the ball can make small aim error look less noticeable (see image).
In doing this you’re ensuring that you’re training your perception of ‘square’ at the address position. How your putter looks when it is aimed accurately down your intended start line. Secondly, if you’re hitting putts through a gate; you're now testing your putting stroke’s competence in start line (not adding aim error into that mix).