To brine the turkey, place water, kosher salt in large container. Stir well, add turkey, cover with water and allow to brine at least 5 hours or overnight.

Press Saute on Instant Pot. Add oil.

When hot, add chopped onions cook for about 3 minutes.

Add garlic, celery, carrots and herbs, cook for another 3 minutes. If things are getting too dry use the olive oil sprayer and add some more oil.

Add rack to Instant Pot over broth and place turkey on rack.

Set to manual pressure on high for 25-30 minutes. (For 6 lbs, do 25, 7 lbs do 30). Set knob to sealing. Allow to natural release for 10-15 minutes. Then release pressure. Check the temperature with a cooking thermometer -  it should be at least 162 or 163°. (After resting it will go up to 165°).If it's not, set the pressure cook again for another few minutes.

If you like your turkey brown and crispy, place turkey on a baking sheet. Pat the turkey down with paper towels. Use an olive oil sprayer, spray the top, then put in the broiler for a few minutes.

To make gravy: Place a sieve over a bowl and strain off vegetables and any turkey parts.  Place 2 c. broth back into Instant Pot liner. Add 1 T. butter. 

Press, "Sauté".  

In a small cup, add about 3 T. broth.  Add cornstarch. Stir well.

Pour cornstarch mixture into broth.  Cook until thickened. (If you want more gravy, then use all of the broth and add another tablespoon of cornstarch to the cup if needed). Season with salt and pepper to taste.