Lightly grease the insert of a 4- to 6-quart~ Slow Cooker with 1 tbsp butter or coconut oil or a quick spray of Cooking Spray to prevent sticking.

Add the 2 cups old-fashioned rolled oats do not use quick oats or steel-cut, 4 cups water, 1 cup milk whole, 2%, or milk of choice (oat, almond, coconut), 2 tbsp maple syrup or honey, 1 tsp vanilla extract, 1 ½ tsp ground cinnamon, ¼ tsp ground nutmeg, ½ tsp fine sea salt, and 1 tbsp butter or coconut oil to the Slow Cooker. Stir everything together until well combined.

Pick your oat type first — it sets your liquid ratio. Rolled oats: 1:2 ratio (e.g., ½ cup oats to 1 cup liquid). Steel-cut oats: 1:3 or 1:4 ratio. Measure liquid into the Pot before adding oats. Use water, milk for creaminess, or stock for savory bowls. Add a pinch of salt to the liquid. No soaking needed for rolled oats; steel-cut can soak overnight to cut cook time, but it's optional.

Bring measured liquid to a boil over medium-high to high heat (lid on speeds this up). Once boiling, diverge by type. Rolled oats: Stir in oats and salt, reduce heat to low, simmer ~5 minutes, stirring occasionally. Done when liquid is mostly absorbed and texture looks soft and cohesive. Still 4 cups watery? Simmer a few more minutes. Steel-cut oats: Reduce to a gentle simmer, stir in oats, cook 20–25 minutes (Irish-style up to 30), stirring every few minutes. Done when grains are tender with a slight chew. Too thick before fully cooked? Add a splash of 4 cups water. All types: Keep heat at a gentle simmer after adding oats — no rolling boil. Stir regularly to prevent scorching. If you smell burning, start over; the flavor is already ruined.

Give the oatmeal a good stir — it will thicken as it sits. If it's thicker than you like, stir in a splash of warm^ 1 cup milk whole, 2%, or milk of choice (oat, almond, coconut) or 4 cups water to loosen it to your preferred consistency.