Put the bacon in a wide heavy-duty 4- to 5-quart pot or Dutch oven and cook over medium heat, stirring occasionally, until just beginning to turn crisp and golden, about 5 minutes. Remove from the heat. Pour off and discard all of the bacon fat, leaving the bacon in the pot. Add the olive oil and onion and cook over medium heat, stirring occasionally, until the onion begins to soften, about 5 minutes. It’s fine if it colors a bit. Add the celery and garlic and cook, stirring occasionally, until the vegetables have softened, about 7 minutes more. Add the clam broth, carrots, tomatoes, tomato juice, potatoes, oregano, bay leaves, 1/4 tsp. black pepper, and the red pepper flakes. Bring to a boil over high heat. Lower the heat to maintain a simmer and cook, uncovered, until the potatoes and carrots are tender, about 15 minutes.
Remove the soup from the heat, wait until it stops simmering (this may take a minute if you’re using a Dutch oven), and stir in the clams and chopped parsley. Discard the bay leaves and season to taste with additional black pepper, if desired.
Crusty bread is the perfect accompaniment.