Hone your ability to start the ball on line as often as you can. When I practice I have my son Eddie stand behind me on an extension of my chosen starting line. From this down-target view he can easily discern the movement of the putter the angle of the face and whether or not the ball starts on line.
As you start the club down keep your left arm straight so that your swing bottoms out under the ball. Let the club “kiss” the grass. No need to carve a huge divot. Don’t “hit” the ball. Accelerate smoothly through impact. Your goal: Reach max speed about four inches ahead of the ball.
so that you can hinge your wrists fully as I’ve done in the far-left photo. But don’t just hinge your wrists. Allow your body to turn away from the target as you do in a full swing. Stop your backswing when the club reaches a position parallel to the ground.