Measure the steel-cut oats and water. Check that the Instant Pot's inner pot is clean and properly seated in the appliance.
Add the oats, water, and salt to the inner pot. Stir gently to distribute the oats evenly. Add cinnamon if you want a warm, spiced flavor.
Secure the lid according to the manufacturer's instructions and set the steam release valve to the sealing position. Select Pressure Cook on High for 4 minutes as a starting method for a standard batch. Cooking settings and results may vary by model.
When the cooking cycle finishes, allow the pressure to release naturally for about 15–20 minutes. Carefully release any remaining pressure according to your appliance's instructions before opening the lid. This resting period helps the oats soften and absorb the remaining liquid.
Open the lid carefully, keeping your face and hands away from escaping steam. Stir the oats thoroughly. They may look slightly loose at first, but they will thicken as they stand. Add a little warm water or milk if you prefer a thinner consistency.
Stir in vanilla extract and maple syrup or brown sugar, if desired. Divide the oatmeal between bowls and add your favorite toppings, such as berries, bananas, walnuts, almonds, or chia seeds.