Combine the oats, rice, millet, barley, wild rice, grits, flaxseed, salt, and water in the slow cooker.
½ cup steel-cut oats, ½ cup short-grain brown rice, ½ cup millet, ½ cup whole-grain barley, ⅓ cup wild rice, ¼ cup polenta or corn grits, 3 tablespoons ground flaxseed, ½ teaspoon salt, 8 cups water