Cut the stump down as close to ground level as you can. This removes excess material from the stump that someone could potentially trip over and helps to ensure that the salt will make it to the roots and not just be distributed through the trunk stump.
Drill into the side of the stump at a downward angle as close to the top of the stump as you can get. Make the hole large enough that you'll be able to pack it with salt, at least 1 inch in diameter. Drill additional holes every few inches around the stump; the larger the stump is, the more holes it should have.
Pack the holes with rock salt, getting as much of the salt into them as you can. If you are not concerned about grass or other plants that surround the stump, you can also place a line of additional rock salt on the ground close to the stump.
Cover the stump and the holes with soil, then cover the soil with mulch. Pour water over the soil and mulch to help dissolve the salt and to pack the soil in around it.
Water the stump every 2 to 3 days for several weeks, or more often during dry conditions, saturating the mulch. This water helps the salt to dissolve and be absorbed by the roots and stump while also encouraging the growth of fungi and other organisms that will decompose the stump.
Check the stump and roots periodically, adding more soil and water if needed to encourage decomposition. If you notice new growth appearing from the roots or around the stump, cut off the new growth and repeat the salting process to deplete nutrients from the wood and kill the stump.
So, I looked it up. Makes sense. You can also fertilize the crap out of it or feed some sort of birds near it (geese, chickens, ducks) to get the nitrogen to kill it. We all know how quick nitrogen will fry plants.
We also used it to pull up the fence posts we were moving. Much better than digging them up by hand!
