My aunt Jeanette would make this every Christmas Eve. I looked forward to it every year! Instead of using "wheat" flour like she does, I just substitute it with featherlight. You don't need any xanthan gum. It thickens just fine. You don't have to picky about how many vegetables you add. Just add about 5 - 6 cups. If you like it chunky add more, if you like it thin add less.
1 cup celery, chopped
1 cup onions, diced
3 cups potatoes, peeled and cubed
1 cup carrots, peeled and sliced
2 cans minced clams
1/2 cup butter
1/2 cup featherlight flour
1 quart half and half
1 ½ teaspoons salt
½ teaspoons sugar
pepper, to taste
2 teaspoons Beau Monde seasoning
2 teaspoons lemon juice
dash GF Worcestershire sauce
Put celery, onion, pototoes and carrots in a large saucepan. Drain the clam juice into the pan with the vegetables. Set clams aside. (If you add them now they can become rubbery.) Add just enough water to cover the vegetables. Cook until tender, about 20 minutes.
While vegetables are cooking, make a rue. In a separate saucepan, melt 1/2 cup butter at medium temperature. Add the flour and whisk. Stir for just a bit, heating the flour/butter mixture. Add half and half. Stir regularly until it thickens and begins to boil. Take off the heat.
When vegetables are soft. Pour the thick cream sauce into the pan with the vegetables. Stir until combined. Add salt, sugar, pepper, Beau Monde seasoning, lemon juice, Worcestershire sauce, and clams. Stir and heat another 4 or 5 minutes. Eat, or keep warm in a crockpot.