Notes: for a beef bone broth, take 3 ½ pounds of mixed beef bones, such as knuckles, short ribs, femur, short ribs and neck bones. Drizzle with a little olive oil and roast at 400 degrees for about an hour, turning once, until the meat and bones are golden brown. Proceed with recipe as indicated above, but cook in slow cooker for at least 24 hours. You can also mix chicken, beef and pork bones together.
If you don't have a slow cooker and want to do this on the stove, bring to a boil over high heat and reduce to a very gentle simmer and simmer until you have to go out or if you want to go to sleep. Then transfer pot, covered, to a 250 degree oven and allow to simmer in the oven as long as you wish.