If you can consistently putt the ball at the correct speed from 15 to 20 foot, you will have more chance of holing putts from this distance.
For this drill place one club 15 foot away from you and another club 20 foot away from you.
Now I would like you to see how many balls you can putt, one after another that finish between the two clubs.
You will need to go through your normal routine to keep it as real as possible.
When one ball doesn’t finish between the clubs change position so you then practice from an uphill, downhill, right to left and left to right breaking putts.
Make a note of how many balls finish between the clubs from the various slopes and each time you practice this drill always try and beat your best score.
As your score improves this will give you a more confident putting stroke and will enable you to hole more putts.