Start by preparing your ingredients: peel and dice the apple, measure out the oats, and gather the spices.
Turn on your Instant Pot and set it to 'Sauté' mode. Once hot, add the apple and sauté for about 2-3 minutes until slightly softened.
Add the steel-cut oats, almond milk, brown sugar (if using), ground cinnamon, and salt to the Instant Pot. Stir to combine.
Close the lid and set the steam release handle to 'Sealing.' Select 'Pressure Cook' (high pressure) and set the timer for 10 minutes.
After the cooking time, allow for a natural pressure release for 10 minutes. After that, carefully turn the steam release handle to 'Venting' to release any remaining pressure.
Open the lid, stir the oats gently, and if desired, add maple syrup to sweeten further.
Serve warm in bowls with your choice of additional toppings, such as nuts, seeds, or dried fruit.