Place five tees around the hole randomly from 8-15 feet. The game starts with the first make. You must make 3 of 5 to pick up the tees. If you make 3 in a row, it's a hat trick. If you make every other putt, it's a leap frog. Make the 3rd putt really, really important so you learn to take the same mindset into every putt you roll. If you move around to different holes, you will see all kinds of different slopes and speeds.
One of the skills lacking in young players is speed control within 15 feet. It is a vital skill for learning to read greens well. If you can't roll the ball at the speed you envision, your feedback for reading putts won't be valid. An added goal of this game would be to have any putt that doesn't fall go 6"-12" past the hole. At that speed, your ball has the best chance of falling into any part of the hole, not just the center.
Finally, make sure you celebrate your makes, especially the third that allows you completion. A grab of the hat, a tightening of the fist or a simple smile would work. When you miss, give a thought to why, learn from it, adjust and let it go. Your goal is to learn and improve. If you aren't improving at any skill, look hard at what you take away from your practice. If you are in the habit of getting angry or sad after a miss, you won't accept it and learn from it. You need to be your best coach and beating yourself up or looking for failure patterns isn't good coaching. Many players bring emotions to their practice and play that get in the way of their improvement. Another Tar Heel said it best:
!The SMU Mustangs will be playing this game next week. It's a great way to practice making that clutch putt for birdie or a par save. Enjoy!