Place parts for soup (necks, backs or sometimes you can buy the bones left over from boneless chicken breasts) on an oven-proof tray with sides. Make sure the parts are in a single layer or use additional trays. My most recent batch was about 40 chicken necks – just to give you an idea of how much I used. Roast at 400 F for about 30 to 60 minutes; you want the parts to get browned, like you’re roasting a chicken, so the timing will vary depending on the size of the parts, whether they have skin on them or not, etc. Move the parts around on the tray from time to time so they all get cooked, on all sides. If a lot of liquid accumulates, remove it from the tray to the soup pot so you don’t get steamed chicken parts. While you’re roasting the chicken parts you can also roast a couple of unpeeled onions and carrots on the tray, too.
Place the chicken parts in pot with onions, carrots, celery leaves, herbs (I use bay leaves, thyme and parsley), salt and water just to barely cover. Use some of the water to remove the browned bits of meat and vegetables that have stuck to the roasting tray and add that to the stock: this will boost the flavor, make the stock a lovely brown color and make cleanup much simpler. You can speed this up by putting the tray with a little water on a warm burner and scraping the pan with a metal spatula.
Cook for about an hour at a simmer: check the seasonings. Strain the stock. If there’s a lot of meat on the bones, remove it and use it for chicken salad or to add to a soup.