Drain the canned clams, reserving all liquid in a measuring cup. Set the clams aside in the refrigerator until needed. If the reserved liquid measures less than 3 cups, supplement with bottled clam juice.

In a large Dutch oven or heavy-bottomed pot, cook the diced bacon over medium heat until crispy, about 5-7 minutes. Remove half of the bacon for garnish, leaving the rest in the pot.

Add the diced onion, celery, carrot, and bell pepper to the pot. Cook in the bacon fat until vegetables begin to soften, about 5-6 minutes, stirring occasionally.

Add the minced garlic and cook until fragrant, about 1 minute, being careful not to burn it.

Stir in the tomato paste and cook for 2 minutes, allowing it to caramelize slightly for deeper flavor.

Sprinkle the flour over the vegetables and stir continuously for 1-2 minutes to eliminate any raw flour taste.

Gradually pour in the reserved clam juice, stirring constantly to prevent lumps from forming.

Add the crushed tomatoes, broth, diced potatoes, bay leaf, dried thyme, and red pepper flakes (if using). Season with black pepper (hold off on salt until the end as clam juice can be quite salty).

Bring the mixture to a boil, then reduce heat to maintain a gentle simmer. Cover partially and cook until potatoes are tender, about 15-20 minutes.

Once potatoes are tender, add the reserved clams and simmer for just 2-3 minutes to heat through without overcooking.

Remove from heat and discard the bay leaf. Taste and adjust seasoning with salt and pepper as needed.

Stir in the fresh parsley and let the chowder rest for 5 minutes before serving.