Using a large stockpot, add the following ingredients:
Chicken carcass, preferably left-over bones and bits from an oven-roasted bird
Yellow onions~ about two
Celery stalks~ three or four
Carrots~ three or so
Herbs~ thyme, peppercorns, salt & bay leaf are essential, plus oregano, parsley, sage, garlic, or other herbs that appeal to you
If you have good leftovers, they can be added too:
~tomato-based sauces, parmesan rinds, fennel, stems from kale, chard, beets, mushrooms, leeks, peas, etc.
*Avoid strong/bitter flavors, such as:
~anything from the cabbage family (brussels sprouts, broccoli, cauliflower), beets, turnips, spinach
Fill the pot with water to cover the ingredients by one inch and bring to a boil; reduce heat to maintain a gently bubbling simmer and cook for three to four hours*.
Strain stock (still hot-warm) through a sieve, pressing on the solids to extract all the goodness.
Boil/simmer remaining broth to reduce and concentrate the flavor. I take it down from 10-25% by volume.
Chill overnight. In the morning the fat will have solidified, making it easy to remove. This is Schmaltz, and can be used as a fat (very low smoking point however) for cooking and baking.
Use, freeze, or can the stock.
*letting the stock cook longer can make it taste bitter and over-cooked, so can letting the stock sit, unstrained, as some herbs turn bitter as they steep.