Prepare the chicken bones for use. Remove leftover meat. Any discarded pieces from a cooked chicken can be thrown in the pot to make the broth/stock (skin, grissle, fat, and bones).
Place roughly chopped onion, celery stalks, and carrots in a large stock pot. You can use any of the trimmings from vegetables that you used for other dishes. Wash the vegetables first, but carrot peelings, carrot stems and greens, celery greens, or any other vegetable trimmings can be added to the stockpot.
Layer vegetables and herbs in the stock pot. Layer the chicken bones on top of the vegetables.
Add salt, pepper, oregano, and any other herbs or seasonings.
Fill the pot with water. You can make as much broth as you'd like so fill it up!
Bring the pot of water to a boil, then turn it down to a simmer and cover with a lid.
Simmer for at least 1 hour, but up to 24 hours. 3-4 hours is a good amount of time to infuse a lot of flavor and nutrients into the broth. Keep the pot covered while simmering so that the water doesn't evaporate. Add additional water while simmering if needed.
When the broth is done simmering, pour it through a strainer to remove all of the vegetable and bone pieces.
Refrigerate in an airtight container for 3-4 days or freeze for up to 6 months.