1. Cook the bacon in a large pot over medium heat until crispy, then remove it and set aside, leaving the rendered fat in the pot.
2. Melt butter in the pot with the bacon fat, then sauté the diced onions, celery, and minced garlic over medium heat until softened and fragrant (about 5 minutes).
3. Sprinkle flour over the sautéed vegetables, stirring constantly, to create a roux; cook for 1-2 minutes to eliminate the raw flour taste.
4. Gradually add clam broth, clam juice, or chicken stock, stirring continuously until smooth, and bring the mixture to a gentle boil.
5. Add diced potatoes, thyme, and bay leaves to the pot. Reduce the heat and let the mixture simmer uncovered for 20-25 minutes, stirring occasionally, until the potatoes are tender.
6. If using fresh clams, clean and steam them until they open, then remove the clam meat from the shells, chop, and set aside. If using canned clams, drain and reserve the clam juice.
7. Stir heavy cream or half-and-half into the pot, along with the prepared clams, allowing the mixture to simmer gently without boiling to warm through.
8. Season with salt, pepper, and optional additions like a splash of red wine vinegar or a dash of hot sauce, adjusting to your taste.
9. Serve the clam chowder hot, garnished with crispy bacon bits, minced parsley, and freshly cracked black pepper. For an ideal pairing, accompany the chowder with oyster crackers or crusty bread.