I don't agree about battery birds, sorry.
I do try to buy free range for health and ethical reasons, but seriously, a battery bird will make a lovely soup, too...
I bung whole chicken carcass (cooked, usually a day or two old) in a large saucepan with 4 cloves garlic, one large onion (quartered), 1 large leek (chopped roughly), 1 large carrot (same), herbs (lots of...fresh or dried - whatever you fancy), 2 bay leaves, salt & pepper. Cover with cold water, bring to boil and then simmer very gently for 2 hours.
Then skim scum off top, add chopped up new potatoes and parsnips and pieces of chicken salvaged from carcass, and simmer for a further one hour.
Then skim scum off again, remove bones and either serve as it is, or whizz in blend with a little bit of single cream and lots of black pepper.
Lovely jubbly.