Set the slow cooker on low heat (if you have settings that let you pick the cooking duration, select the longest one. Mine lets me slow cook for ten hours and then automatically switches over to the “warm” setting; however, I don’t let mine switch to “warm” because I keep resetting the timer round-the-clock – every 10 hours – for a minimum of 48 hours, adding another couple cups of water, as needed to prevent over-evaporation and leave you with a measly amount of broth at the end – and also to keep the broth from tasting burnt). I actually prefer cooking round-the-clock for 72 hours, though, because by then, the bones are pretty much turning to mush. The broth will be rich and hearty, and a delicious golden-brown color – unlike the awful, pale and over-priced pre-made bone broth you get at the store). Note: Some bone broth recipes call for only a 24-hour cook time. Although this is still far better than most broths you’d buy at the store, I prefer to really let those bones leach their nutrients – and that can only happen with time. The bones in the photo below were so well cooked, I could literally crust them between two fingers.