In Instant Pot, add 3/4 cup rice and 3/4 cup cold water. Close the lid, set valve to Sealing and pressure cook on High pressure white rice for 3 minutes and brown rice for 22 minutes. After natural release the pressure for 10 minutes.
While rice is cooking, using the paring knife cut around the tail of each bell pepper and discard seeds using a tablespoon. Set aside.
In a large mixing bowl, add ground beef, cooked rice, onion, oregano, thyme, basil, salt, red pepper flakes and ground black pepper. Using your hands or spatula, mix really well. Stuff peppers with mixture, dividing evenly.
To Instant Pot, add trivet and vegetable stock. Arrange 1 layer of peppers and top with half of the tomato sauce. Lay remaining peppers and top with remaining sauce.
Close the lid, turn release vent to Sealing and press Pressure Cook or Manual on High Pressure for 10 minutes. Release pressure right away by turning the valve to Venting, Quick Release. Or let it subside on its own.
Serve stuffed peppers with their juices from the bottom of the pot (turkey baster is the best to scoop those up), plain yogurt or sour cream and toasted whole wheat or rye bread.
Video
Notes
Store: Refrigerate in an airtight container for up to 3-4 days. Not recommended to freeze.