In a large dutch oven over medium heat, cook the bacon, stirring occasionally until crisp tender (not too crunchy). Using a slotted spoon, transfer to paper towels to drain. Leave the bacon grease in the pan.
To the remaining bacon fat, add the onion, celery, and carrot. Cook while stirring until tender but not browned. Add garlic, sauté for 30 seconds, and then stir in the tomato paste.
Stir in clam juice (reserved juice, and the canned clam juice), potatoes, add a bay leaf, thyme, oregano, and red pepper flakes if using. Stir everything to combine, bring to a boil, reduce heat to simmer and cook for 15-20 minutes or until the potatoes are cooked and fork tender.
Stir in diced tomatoes, clams, reserved bacon, and season with salt and pepper (taste before adding salt as it depends on how salty the clam juice is). Gently simmer for 5 more minutes (if you boil the clams, they can become tough so you just want them to be warmed through).
Discard the bay leaf and serve. Garnish with chopped parsley, serve with oyster crackers.