The easy (if slower) way is to drill the stump full of holes and fill the holes with milk. The milk will jump start the bacteria/fungi that digest/rot the stump. The Amish around me simply cover the stump with horse/cow manure, of which they have plenty.
If you don't want to wait for Mother Nature to do the work, you can use a tree shear. It will cut the stump off at or slightly below ground level.
If you don't want to wait for Mother Nature to do the work, you can use a tree shear. It will cut the stump off at or slightly below ground level.