Stone-ground grits are ground in a stone mill and are much larger than quick- cooking grits. They also have an abundance of flavor compared to the faster-cooking versions. Most Southerners will put them on the stove and cook them for hours, sometimes even all day, while popping in and out of the kitchen to stir. Cooking them in the slow cooker requires no stirring at all. Let them cook all night and wake up to rich, creamy grits.
Lightly spray a 6-quart slow cooker with nonstick cooking spray.
Place the grits in a medium mixing bowl and cover with water to rinse any debris. Stir gently and skim off any debris that floats to the top. Drain the grits and discard the water.
Add the grits, 3½ cups of water, the milk, butter, and salt to the slow cooker. Turn the slow cooker to the low setting, replace the lid, and allow to cook for 6 hours. Stir the grits well before serving.