In a large pot, slowly cook bacon over medium-low heat until crisp. Remove crispy bacon with a slotted spoon and save.
Add onions and celery to the bacon drippings and cook until soft, about 10 minutes. Add pepper, thyme, and garlic. Cook 1 minute more. Turn heat to medium-high, add flour, and stir to make a light brown roux, about 3 minutes.
Add clam broth and fish stock, whisking out any lumps and combining everything thoroughly. Bring to a boil and add potatoes. Lower heat back to medium-high and simmer until potatoes are cooked through, about 15 minutes.
Stir in chopped clams, cooked bacon, and cream. Heat soup to hot being sure not to let it boil. Serve in large soup bowls with oyster crackers, salt, pepper, and Tabasco or another hot sauce on the side.