Add the oats, pumpkin, almond milk, water, pumpkin pie spice, vanilla, salt and maple syrup to a slow cooker and stir to combine.
Place the lid on the slow cooker and cook on low for 8 hours.
Serve immediately or transfer to an airtight container and store in the refrigerator for up to 5 days. Can be frozen in a airtight container for up to 2 months.