Place a large pot over over medium high heat.
Add 1/4 cup (1/2 stick) butter.
When butter has melted and is hot (do not burn), add carrots, onions, celery and potatoes. Sauté vegetables until tender, about 5 minutes.
Add water, clam base, clams, white pepper, bay leaves, thyme, oregano, Old Bay Seasoning and basil. Heat to boiling, stirring occasionally. Reduce heat to a simmer.
Place a medium saucepan over medium heat.
Add remaining 1/2 cup (1 stick) butter.
When butter is melted, stir in flour until all flour is coated with butter. Using a wire whip, gradually add some water from the vegetables to the mixture in the saucepan. Mix well to make a roux.
Add roux to the vegetable mixture. Stir until smooth and thickened, about 2 minutes.
Taste. Add salt and pepper, to taste.
Simmer until desired consistency.
Remove bay leaves.
Serve hot.