Saute Bacon: Place bacon in the Instant Pot, and then turn on the Saute function. Fry the bacon until crisp, about 7-9 minutes. Remove to a paper towel-lined plate, leaving the bacon grease in the pot.
Saute Aromatics: Next, add the onion and celery and saute until softened, about 5 minutes. Stir in the garlic during the last 30 seconds.
Additional Ingredients: Place a colander over the Instant Pot and drain the clams, adding the juices to the pot. Set the clams aside in a bowl. Stir in the bottled clam juice, potatoes, thyme, bay leaves, 1/2 teaspoon salt, and 1/4 teaspoon pepper to the cooker.
Pressure Cook: Lock and seal the lid. Cook for 6 minutes at high pressure with a quick release of the pressure. Remove the bay leaf.
Thicken Soup: Turn on the Saute function. In a small bowl, stir together the cornstarch with 2 tablespoons of water until smooth. Add this slurry to the soup and stir until thickened, about 2-3 minutes. Press Cancel.
Finish Soup: Stir the half and half and clams into the pot. Taste and season with more salt and pepper, if needed. The soup will thicken up more as it cools off.
Serve: Serve warm in bowls topped with minced chives, bacon bits, and oyster crackers.