In a large stockpot, over medium heat, fry bacon until crisp. Stir in leeks, celery, and carrots, season with salt and pepper, and add bay leaves. Cook, stirring, until vegetables are soft and tender, about 10 minutes. Stir in flour and cook for 10 minutes, stirring occasionally. Add clam juice, potatoes, and corn, season with salt and pepper, reduce the heat to medium-low, and simmer until potatoes are fork tender, about 15 minutes. Add cream, parsley, and clams and their liquor and simmer for 5 minutes. Remove bay leaves. Ladle into soup bowls and serve hot with oyster crackers.