Roasted chicken bones
Sad veggies, just past their prime
Water to cover
Salt and Pepper
Put all in a Crockpot on low for at least 8 hours. Set it and forget it.
You'll have to spend time later straining the bones and the veggies out (I don't care for soft veggies in my soup but they do add a nice flavor to the broth) Tip: put a colander inside a larger pot and pour crockpot contents into it. Remove colander. Later you can add diced potatoes, (better-looking) veggies, and/rice or pasta to make a soup or use as a base for another dish, like rice pilaf.
Suggestion: you can compost the cooked veggies. If you have a bokashi composter, you can compost the whole thing!