Place the frozen chicken in a single layer in the pot. Pour in enough water to cover the chicken without filling above the "MAX" line. More water will yield a greater quantity of milder broth.
Sprinkle in the salt, garlic powder, pepper, thyme, and celery salt. Place the onion quarters around the chicken.
Close the lid and seal the vent. Cook on high pressure for 30 minutes.
Allow natural pressure release for 10 minutes, then manually release any remaining steam.
Use an instant-read thermometer to verify the chicken is at least 165°F throughout.
Transfer the cooked chicken to a bowl with tongs or a slotted spoon. Let rest 5 minutes before serving or shredding.
Place a fine mesh strainer over a large measuring cup and strain the broth. Transfer the broth to glass jars.