Setup:
1- Set up 4 tees again, each one 3 feet from the hole, 90 degrees apart from each other. This is your safety box.
2- Now take 2 balls and choose a spot 20 feet from the hole. (About 7 paces)
Drill:
1- Putt the 2 balls and stop them within the safety box.
2- Repeat from a different spot, still 20 feet from the hole.
3- Continue until you get 10 in a row in the safety box.
4- If you miss one, start over.