Put the chicken carcass in the slow-cooker. Add all the remaining ingredients and turn on low.
After 12 hours you can basically use the broth but the longer you let it steep the more the collagen comes out of the bones. The apple cider also helps with this.
After 20 hours you strain the liquid. You can now let it cool and freeze it until you need it. In refrigeration, you will notice that the broth thickens. This is normal. When you heat it, it will become liquid again. It's the gelatin that thickens it.