Place the beef bones, onions, carrots, and celery in a roasting pan and bake in a preheated 500F (260C) oven, turning everything once or twice, until browned, about 30 minutes.
4 lbs beef bones, 2 medium onions, 2 large carrots, 2 ribs celery
Combine the bones and vegetables and the remaining ingredients in a large pot over high heat and bring to a boil.
4 quarts water, 1 bunch parsley, 1 leaf bay, 1/2 tsp dried thyme, 12 whole peppercorns, 2 whole cloves, Salt
Reduce the heat and simmer covered for 3 hours.
Strain the stock, pressing on the meat and vegetables to extract as much liquid as possible. Refrigerate and skim off and discard the fat that congeals on the surface.
Keep refrigerated for up to 4 days, or freeze for up to 1 year.