Place vegetables in a double layer of cheese cloth and secure in a bundle with the cooking twine (see image below)Put bones and vegetables into the slow cooker and top with water until covered.Cook in LOW for 24 hours (you can leave for slightly longer or less).After an hour or so, skim any "gunk" that is floating on the top. Organic/cleaner meat will yield much less of this.Remove top and let cool slightly.Place strainer over a bowl and ladle broth into strainer to separate bones and vegetable bundle from the liquid.Season with salt and pepper as desired.