Apple Cinnamon Steel Cut Oats

2 apples, peeled, cored, cut into 1/2-inch pieces (2-1/2 to 3 cups chopped)
1-1/2 cups fat-free milk (or substitute non-diary alternative like almond milk)
1-1/2 cups water
1 cup uncooked steel-cut oats
2 tablespoons brown sugar (or substitute maple syrup or other desired sweetener)
1-1/2 tablespoons butter, cut into 5-6 pieces (optional)
1/2 teaspoon cinnamon
1 tablespoon ground flax seed
1/4 teaspoon salt

Optional garnishes: chopped nuts, raisins, maple syrup, additional milk or butter

Directions
Coat inside of 3-1/2 quart (or larger) slow cooker with cooking spray. Add all ingredients (except optional toppings) to slow cooker. Stir, cover, and cook on low for approx. 7 hours (slow cooker times can vary). Spoon oatmeal into bowls; add optional toppings, if desired. Store leftovers in refrigerator. Freezes well.

To reheat single servings: Put 1-cup cooked oatmeal in microwave proof bowl. Add 1/3 cup fat-free milk. Microwave on high for 1 minute; stir. Continue cooking for another minute, or until hot.

Recipe can be doubled in 6-quart or larger slow cooker. Increase cooking time 1 hour.

NOTES:

• This recipe was a creamier texture than the other one I tried.
• It made 4 generous servings (could also be 5 smaller ones).  We ate two right away and refrigerated the other two for later in the week.  It was better fresh, but microwaved just fine too.
• I can't remember what kind of apple I used, but it was pretty bland.  I'd try something like a granny smith next time.
• I bought a small crock pot just to try this recipe, but it seems to have a hot spot (evidenced by the very overcooked corner of things).  I'm going to return it and try a double boiler method in my regular crock pot next time.  (see below)
• Source
• UPDATES: I used the double boiler method below and it was perfect.  I also used two unpeeled granny smith apples this time and the apple flavor was much more pronounced.  I'd recommend both of these and will be making this recipe regularly throughout the winter.
• Makes 5-6 servings and reheats well in the microwave.

Double Boiler Method:  (Source)

You can completely avoid burnt oatmeal edges and cook it for an extended time by turning your slow cooker into a double boiler. It's easy.

Find a heat-proof bowl that will nest inside your slow cooker.

Coat the inside of the bowl with cooking spray.

Add water to the slow cooker on the outside of the bowl, until it reaches approx. half way up the side of the bowl.

Add the oatmeal ingredients to the bowl, and stir.

Put the lid on the slow cooker and cook on low for up to 8 hours (it was ready sooner, but it held for 8 hours)

This method worked great for me. I had my slow cooker on for 8 hours of cooking, and then it went to the warm mode for awhile after that. There were absolutely no browned or burnt edges. The texture of the oats was perfect. Another benefit of this method--clean up is a breeze! I put the bowl in my dishwasher and dumped the water and dried inside of slow cooker with a towel--done!