Spray the insert of a slow cooker with cooking spray. Add oats, brown sugar, vanilla bean, cinnamon, nutmeg, and cardamom.
Add 3 1/2 cups water.
Cook on LOW for 8 hours.
After 8 hours, add 1 cup almond milk to thin out the oatmeal. Add more to get the consistency that you like. If you enjoy runnier oatmeal add more almond milk.
Spoon oatmeal into a bowl.
Add raspberries, blueberries, and blackberries. Sprinkle with almond flakes and additional brown sugar if desired. I like to add an extra splash of almond milk before I serve it.
Serve with a steaming cup of coffee and enjoy the rest of your day. This recipe is adapted from Pure Vanilla (which happens to be a great cookbook and one worth having if you love vanilla like I do).