The best way that I was taught is to take one cup of rock salt and two cups of water. Put your hering in the mix and place in the freezer until you want to use them. The water will not freeze if the mix is correct and your herring will last a long time, as long as when you are fishing, you keep your container in a cooler. I have had herring last 2 months in the freezer and fished with it with no problems.