Rinse the long-grain brown rice under cold running water in a fine-mesh sieve until the water runs clear.
Transfer the rice to the Instant Pot, then pour in the cold water (or vegetable stock) and add the salt. If you like, add the olive oil.
Close the lid and set the steam release valve to Sealing. Select Pressure Cook (high pressure) and set the timer for 22 minutes.
Once the cooking cycle has finished, allow the pressure to release naturally for 10–15 minutes, then carefully switch the steam release valve to Venting to release any remaining pressure.
Open the lid away from you, fluff the rice with a fork and serve immediately, or store any leftovers in an airtight container.