1) Fill a gallon ziplock bag or gallon container with vegetable scraps (like onion, carrot and potato peels, celery ends, vegetables, herbs that are about to go bad etc.). Keep in the freezer until it's full and you're ready to make stock.
2) Pour frozen vegetable scraps in a large pot and add 5 cups of water to the pan. Cover and simmer over low heat for a few hours (2 - 4 hours). You can also cook in a crockpot for a half a day on low or shorter on high.
3) This recipe yields about 6 cups if you cook the vegetables with the lid on the whole time on simmer. Cook without a lid for some of the cooking time to get a more concentrated stock and less volume.
4) Drain the cooked stock mix through a strainer into a bowl. Discard the leftover vegetable sludge and use the stock to make whole grains, soups, and any recipe that calls for stock or broth. Add salt to taste.