Our practice green has a really small hole cut in it. It's barely bigger than a ball. The drill is to sink two putts in a row from 1 ft, 2ft, 3ft, 4ft, and 5ft. As long as you make one out of two putts from a given distance, you can stay there until you make two in a row. If you fail to make at least one out of two, you go back to the beginning.
After getting two in a row from 5 feet in the small hole, I went to a standard sized hole and did the same drill, this time extending well beyond 5 feet (in one foot increments).
If you don't have a small hole on your green no problem, just use a regular hole.