I keep a bin of carrot ends, celery ends, onion ends and skins in the freezer. When it's Costco Rotisserie Chicken Day, we eat the chicken, then throw the freezer bin of stock vegetables in the pot as well. To this add as many celery sticks, carrots, and onions as you like. You're looking at maybe 3 carrots, 4 celery sticks, half an onion or so, total vegetables.