Drain the clams and save the juice: Set a strainer over a measuring cup and drain all three cans, keeping the clams in the fridge until the end. Add the bottled clam juice to the same cup. You should have about 2 1/2 cups of liquid.

Crisp the bacon: Cook the chopped bacon in a large Dutch oven over medium heat for 7-8 minutes, stirring, until browned and most of the fat has rendered. Lift half of it out onto a paper towel for garnish and leave the rest in the pot with the drippings.

Soften the vegetables: Add the butter, onion, and celery and cook for 5-6 minutes, until the onion is translucent. Stir in the garlic and cook 30 seconds more.

Make the roux: Sprinkle the flour over everything and stir constantly for 1-2 minutes, until the vegetables are coated in a thick paste and the raw flour smell is gone.

Add the liquid and potatoes: Pour in the clam juice a splash at a time, whisking after each addition so no lumps form, then whisk in the chicken broth. Add the potatoes, bay leaf, thyme, salt, and pepper and bring it up to a gentle simmer.

Simmer until the potatoes are tender: Simmer uncovered for 15-20 minutes, stirring now and then, until a fork slides into a potato cube with no resistance. The broth will thicken noticeably in this stretch.

Stir in the half-and-half: Turn the heat to low, pour in the half-and-half, and warm for 3-4 minutes. Keep it below a simmer, because boiling dairy can separate and turn the chowder grainy.

Add the clams and serve: Stir in the drained clams and heat for 2-3 minutes, just until the pot is steaming and reads 165°F. Canned clams come fully cooked, so this is reheating, not cooking, and any longer turns them rubbery. Fish out the bay leaf, then top each bowl with the reserved bacon, parsley, and oyster crackers.