Put the thyme, parsley and peppercorns into a spice ball. In a 6 qt Instant Pot, add the water and then all of the ingredients, starting with the chicken pieces and finishing with the onions.
Cook on the Soup setting for 1 hour. If you are doing this on its own day, feel free the let the pressure naturally release. If you want it all done in one day, natural release pressure for 10 minutes, then use cold wet clothes on the metal parts of the lid to hurry up the rest of the pressure release. Do not use the quick release valve because the stock will spew out of the vent.
Once the pressure has released, remove the lid. Compost the onions and the leeks. Put the carrots and celery in a dish to eat as you move on the remove the chicken pieces and the bones.
Using a fine-mesh strainer, pour the stock through it into a mixing bowl.
Set aside two cups of the stock for the Matzoh balls. Refrigerate both quantities of stock for at least 3 hours so you can easily skim off the fat if you want to use it in your Matzoh Balls and/or freeze it for future use.
If you want to, separate the chicken meat from the bones and save it for later use in sandwiches, or whatever.