If you currently don’t use a preview stroke try it — and give it a least a month. Always make your preview strokes while focusing on your aim line and visualizing the putt’s roll from start to finish.
In both cases the key is to adjust your shoulders so that they sit parallel to the slope you’re standing on while maintaining good balance so you can swing through the shot. A good practice swing is essential so you can “see” where your swing is bottoming out and making a divot. Use the divot’s location to confirm that you’ve positioned the little white ball in the right spot (i.e. before your wedge strikes the big green one).
This change in grip position effectively shortens the clubshaft and takes a slight amount of power out of the swing making it a little easier to keep greenside shots under control.