Dump cider into a large stock pot. Place on the stove over low heat.
Place salt, spices, and brown sugar on a square of clean cheesecloth (or any clean thin cotton fabric). Pull up edges and tie with a string to form a bag. Place bag in the cider and simmer for at least 20 minutes (but you can let it simmer for a couple hours- that's what makes your house smell really good!).
If you cook this in a crock pot, cook on low for about 2-3 hours, then keep warm.
Refrigerate leftovers and reheat as needed.
Notes
Store the apple cider in a tight locked container and keep it in the fridge for another time.