Start by setting your Instant Pot to the 'Sauté' function. Add the olive oil and allow it to heat up for about a minute.
Once the oil is hot, add the chopped onions and minced garlic. Sauté for about 2-3 minutes until the onions are translucent.
Next, add the sliced carrots, diced potatoes, and the chicken thighs to the pot. Stir to combine.
Pour in the chicken broth and stir in the dried thyme, rosemary, salt, and black pepper.
Secure the lid on the Instant Pot, making sure the vent is closed. Press the 'Cancel' button to stop the sauté mode, then select the 'Pressure Cook' or 'Manual' setting. Set the timer for 15 minutes on high pressure.
Once the cooking time is complete, allow the pressure to release naturally for about 10 minutes before quick-releasing any remaining pressure.
Open the lid, and stir in the frozen peas. If you prefer a thicker stew, mix the cornstarch with water to create a slurry, then stir it into the stew and let it simmer for an additional 5 minutes on the 'Sauté' mode until thickened.
Taste and adjust the seasoning as needed, then serve hot and enjoy!