Instead of using a putter, putt with a nine-iron or a wedge that has a relatively flat leading edge (sand wedges often have curved leading edges). Hold the club the way you normally would a putter. The stroke has to be more precise than with a putter because to get the ball rolling the way it should, without a bounce or a lot of immediate overspin, you have to strike it precisely on the equator with a slightly ascending blow. To do that, you’ll find that everything has to be in order: your hands relaxed, your clubhead accelerating just so. It’s the acid test of a great relaxed putting stroke, and it’s good practice any time.