Prepare the apples by slicing and coring them-- no need to peel, unless you want to.
Place the sliced apples and water in the bowl of your slow cooker, then cover and set to cook on low for 6 hours, until the apples are very soft. (If you have a VitaClay, like I do, it only takes 2 hours on the "stew" setting.)
Use an immersion blender to puree the applesauce, or transfer the apples in batches to a blender and (carefully!) blend using a dishtowel to cover the vent at the top. If you're using a Vitamix, or another high-speed blender, be careful not to over-blend this sauce-- it can become too smooth very quickly. Store the applesauce in the fridge for a week, or freeze for up to 6 months.