In a heavy stock pot, over medium-high heat, render the bacon until crispy, about 8 minutes. Stir in the leeks, onions, celery, and carrots. Saute for about 2 minutes or until the vegetables start to wilt. Season the vegetables with salt and pepper. Add the bay leaves and thyme. Stir in the flour and cook for 2 minutes. Add the potatoes. Stir in the clam juice. Bring the liquid up to a boil and reduce to a simmer. Simmer the mixture until the potatoes are fork tender, about 12 minutes. Add the cream and bring up to simmer. Add the clams and simmer for 2 minutes. Stir in the parsley. Season with salt and pepper if needed. Ladle into serving bowls and serve.