Completely dry the chicken and then cut into 1-2 inch pieces. Grate 1 tablespoon of fresh ginger and set aside. Mince 3 garlic cloves and set aside.
Turn the Instant Pot on SAUTE mode. Add the vegetable oil and let heat up for 30 seconds. Add the chicken to the pot and cook until all sides are browned, stirring as needed.
Once chicken is cooked, deglaze with a bit of the orange juice, scraping the bottom of the pot to remove any chicken stuck to the pot.
Turn off the Instant Pot by hitting the CANCEL button.
Add the rest of the orange juice, ginger, garlic, soy sauce, brown sugar, and rice wine vinegar. Stir everything together.
Place the lid on the Instant Pot and set on MANUAL mode for 5 minutes.
Once the Instant Pot has counted down the 5 minutes and beeped, let the chicken sit for 10 minutes with the lid on and complete a NATURAL RELEASE of the steam for the 10 minutes. After 10 minutes, QUICK RELEASE any remaining steam and then remove the lid.
Combine the cornstarch and water and stir together to create a cornstarch slurry.
Turn the Instant Pot on SAUTE mode and add the cornstarch slurry to the pot. Stir in to combine. Cook for 3 minutes, then turn off the Instant Pot. Let stand for 5 minutes for the sauce to thicken.
Top with freshly grated orange zest. Serve with rice and broccoli, if desired.