Preheat the oven to 325 degrees F. Whisk the cooled melted butter and flour together in a glass baking dish. Bake for 25 to 30 minutes, or until golden and crumbly. Set aside to cool. Dice the potatoes into bite-sized cubes.
Melt 1 to 2 tablespoons of butter in a large stockpot over medium heat. Add the celery, onion, and leeks. Cook for 3 to 5 minutes, stirring occasionally, until soft and slightly translucent.
Add the potatoes, pepper, salt, thyme, bay leaves, Tabasco, chicken broth, and clam juice. Bring to a gentle boil, then reduce the heat and simmer for about 10 minutes, or until the potatoes are fork-tender.
Crumble the baked butter and flour mixture into the pot. Stir until completely incorporated. The chowder base will be extremely thick at this point.
Remove the pot from the heat and slowly stir in the half-and-half until smooth. Return the pot to low heat and warm to serving temperature, stirring often. Do not boil.
Remove the bay leaves. Stir in the clams and heat only until warmed through. Serve immediately and garnish with oyster crackers, crumbled bacon, fresh parsley, homemade croutons, or a sprinkle of Old Bay seasoning.