"Putt around the clock" must be amongst the 5 best/top putting drills: place 8-10 balls in a circle around a hole. Sink the putts and if you miss go one back, continue till all balls are in the hole.
Advanced version: sink 8-10 in a row or start over
My winter/inside version of it is to putt (on my 9 feet putting carpet) 12 in a row or start over.