In a heavy large round Dutch oven, over medium-high heat, render the bacon until crispy, about 8 - 12 minutes.
Using a slotted spoon remove the bacon from the Dutch oven to a plate or bowl, leaving behind the bacon fat in the Dutch oven.
Stir in the leeks, onions, celery, carrots, and garlic, and season with salt and pepper. Sauté until the vegetables start to wilt, about 4 minutes.
Add in the bay leaves and thyme sprigs, and sauté for 30 seconds to 1 minute.
Stir in the flour and cook for 2 minutes.
Add in the potatoes, and stir in the clam juice.
Bring the liquid to a boil, then reduce to a simmer and cook the mixture until the potatoes are fork tender, about 12 - 17 minutes.
Stir in the heavy cream and bring up to a simmer.
Pick out the thyme sprigs and bay leaves.
Fold in the clams and bacon and heat through for 2 minutes.
Stir in the parsley.
Taste and adjust the seasoning if needed.
Ladle into serving bowls, or bread bowls and serve with oyster crackers if desired.