Note: I don't recommend using any other type of oats with this. Steel cut oats seem to stand up to long cooking times far better than other styles of oats. Also, if you prefer your raisins chewy, add them after cooking. Cooking them makes them very soft. However, if you do not cook them with the oats, you will most likely need more sweetener.
Combine the oats, water, cinnamon and vanilla extract in a small, 1 or 2 quart slow cooker. No larger. (You will need to multiply the recipe for larger slow cookers)
Cook on low for 8 hours.
Stir in the raisins OR cranberries and maple syrup when serving.