Quarter the onion and slice the garlic bulb in half.
Place the trivet rack into the Instant Pot then add the onion, garlic and fresh herbs.
Season the chicken all over with salt and pepper, including seasoning the cavity.
Stir together the oil, lemon juice and seasonings.
Brush the seasoning oil over the chicken.
Add the chicken to the Instant Pot then pour in the chicken stock.
Close the Instant Pot lid, making sure the vent is in the sealing position.
Pressure cook on high pressure for 18 minutes and quick-release the pressure.
At this stage, you can serve the chicken as is or use to shred into soups, salads, sandwiches etc. but I prefer broiling it for 10-15 minutes to crisp the skin and add some color before serving.
Carefully remove the chicken from the pot then place in a baking dish, drizzle with a little oil and broil until golden brown for 10-15 minutes.
Optional: Pour the leftover stock through a strainer into a small saucepan. Whisk together 2 teaspoons cornstarch with 2 teaspoons water and stir into the stock. Place over medium heat and allow to simmer until thickened. Serve the gravy with the cooked chicken.