Pour minced clams in their broth, clam juice, milk and butter into crock pot. Add garlic powder and salt and pepper to taste. You can also add onion powder if you feel it needs it. Peel and dice potatoes dice celery and onion and add to the crock pot. Turn on low and cook all day. ( Making the rue.) About an hour before dinner time you will mix some corn starch with a little milk. mix untill it is no longer bumpy. You can do this in a coffee cup with a fork to make it a bit easier. You only need a small amount of this mixture so don't go overboard, just a Tablespoon of corn starch or so. Once the mixture is smooth you can then add it a little at a time to the crock pot and stir it in well. This will thicken your broth, how much you add will determine how thick your broth will be. Personally I like my clam chowder to be on the thick side.