Put the oil in the instant pot insert and press the Saute button.
To the pot add the celery, carrots, onion and garlic. When they have sauteed for about 1 to 2 minutes, add the chicken carcass and the herbs. Stir well. Turn off the IP.
Add however much water will fill your IP insert 2/3 of the way full (see notes above).
Place the lid on securely and close the vent.
Press the Manual button and adjust it to 30 minutes.
Do a natural release when the 30 minutes is up. This will take about and additional 15-20 minutes. (i.e. - do not open the vent for a "quick release"). Just leave it alone for the extra time so the steam can release naturally on it's own.
Open your lid carefully. Season the broth with salt and pepper to your liking.
Place a large mesh colander over a large pot and pour the entire contents of the IP insert through the strainer. Life the strainer out and you should be left with a pot of beautifully seasoned chicken broth.
Divide the broth into food safe containers and store in the fridge up to 3 days or freezer up to 6 months.
Please note that the nutrition data below is a ballpark figure. Exact data is not possible.