Turn the Instant Pot to sauté mode. Once hot, add oil and then add the chicken pieces in a single layer. Let them cook undisturbed for 2 to 3 minutes to lightly brown, then stir and cook another 2 minutes.
Add orange juice, soy sauce, brown sugar, ketchup, rice vinegar, garlic, and ginger. Stir well and scrape the bottom of the pot to remove any stuck bits.
Turn off sauté mode. Close the lid and set the valve to sealing. Cook on high pressure for 5 minutes.
Once cooking is complete, carefully perform a quick release. Open the lid after the pressure is fully released.
In a small bowl, mix cornstarch and water until smooth. Turn sauté mode back on and slowly stir in the slurry.
Let the sauce simmer for 2 to 3 minutes, stirring often, until it thickens into a glossy coating that sticks to the chicken.
Turn off the heat. Let the chicken sit for 1 to 2 minutes to allow the sauce to settle and thicken slightly more before serving.