Fill a large bowl halfway with ice water and add 1 teaspoon of coarse sea salt per 1 cup water. Add the four (3-inch) marrow bones and refrigerate for 12 to 24 hours, changing the water every 4 hours and replacing the salt each time.☞ TESTER TIP: Some testers have asked us, "Do I need to soak the bones?" The answer is yes. This removes the blood and any impurities from the marrow.