Clean off all useable meat from two rotisserie chickens. Place the bones, skin and other bits and juices into the Instant Pot.
Cut celery, carrots and onion into large pieces. Add to the Instant Pot.
Add Chicken Base.
Add water to Max Fill Line. Place lid and steam valve in locked positions. Push pressure cook button. Set time to 1:05. Press Start. Make sure the warm function is also turned on. This will keep the broth warm after it finishes cooking.
When the Instant Pot has finished cooking, let it naturally release the pressure by sitting for 20-30 more minutes. Then release the pressure valve and remove lid.
Strain any bits out of the broth and store in containers for future use. Can be frozen or refrigerated as needed.