Select the Sauté setting on the Instant Pot and heat the avocado oil. Using tongs, place the chicken pieces in a single layer in the pot and cook, flipping once, for about 5 minutes on each side, until browned. Don’t worry if some skin sticks to the pot. Add the celery, carrots, onion, garlic, salt, peppercorns, and bay leaf to the pot and then the water, pouring slowly to prevent splashing. Make sure the pot is no more than two-thirds full.