Place the steel cut oats, salt, and milk/water in a greased (either butter or cooking spray) slow cooker and whisk to combine.
Cook for 2-3 hours on high or 4-6 hours on low. Stir everything around once or twice during the cooking process.
Optional add-ins
If you'd like to dress this oatmeal up a bit, feel free to add spices and/or sweeteners of your choice along with all of the other ingredients. I generally don't add any of the suggested toppings until I'm ready to eat.
Notes
Notes: Cow's milk, almond milk, water, and a combination of any of those 3 work well. Other non-dairy milks—such as coconut—may also work, though I haven't tried using them.