Trim excess fat from the chicken thighs and pat them dry.
In a small bowl, combine 2 teaspoons olive oil, lemon zest, lemon juice, 2 teaspoons minced garlic, 1/2 teaspoon salt, 1/4 teaspoon black pepper, and 1/2 teaspoon Italian seasoning; rub the mixture evenly over the chicken.
Set the Instant Pot to Sauté (normal) and heat 1 tablespoon olive oil until shimmering.
Sear the chicken thighs 2–3 minutes per side until browned but not cooked through, then transfer them to a plate.
Add half of the chicken stock to the pot and scrape up any browned bits from the bottom, then add the remaining stock and any reserved lemon juice/zest.
Place the trivet in the Instant Pot and arrange the seared chicken on top of the trivet.
Close the lid, set the pressure valve to sealing, and cook on Manual/Pressure Cook at HIGH pressure for 7 minutes.
When the cooking cycle finishes, turn off the cooker and allow a natural pressure release until the pin drops, then open the lid away from your face and remove the chicken to a plate.
To make gravy (optional), mix 2 teaspoons cornstarch with 1 tablespoon water in a small bowl to make a slurry, set the Instant Pot to Sauté, stir the slurry into the cooking liquid, and simmer until thickened.
Serve the chicken with the pan sauce if desired.
