Pour the cranberries into a colander and rinse them under cold water. Pick out any soft, mushy, or shriveled ones. Keep the firm, plump berries so your sauce tastes fresh and clean.
Pour the cranberries into the crockpot. Add the orange juice, water, and maple syrup. If you want the optional spices or zest, add them now too.
Give everything a good stir with a wooden spoon. Make sure the sweetener dissolves into the liquid and no berries stick to the sides. A well-mixed pot cooks more evenly.
Cover the slow cooker and cook on high for 3 to 4 hours. You can also use low for 7 to 8 hours if you are away all day. You will know it is done when the berries pop and the sauce bubbles.
Open the lid and stir the sauce gently. Taste it and add a little more sweetener if it feels too tart. This is also the time to stir in extras like walnuts, vanilla, or a splash of bourbon.
Serve the sauce warm, or let it cool a bit first. It thickens a lot as it cools, so do not worry if it looks loose at first. I like to spoon it into a pretty bowl and chill it if I am making it early