Combine salt pork or bacon and 1/4 cup water in a heavy-bottomed stock pot or Dutch oven. Over medium heat, stirring occasionally, until water has evaporated and pork has begun to brown and crisp in spots, about 8 minutes. Add butter, onion, and celery. Continue to cook, stirring occasionally, until onions are softened but not browned, about 4 minutes longer. Add flour, cook another minute. Add milk and clam juice, stir until it begins to thicken.
If using raw clams, steam with simmering water until opened, then allow to cool. Remove clams from shell and roughly chop.
Add potatoes, bay leaves, and a pinch of salt and pepper to the pot. Bring to a simmer, and cook, stirring occasionally, until potatoes are tender and starting to break down, about 15 minutes. Add heavy cream, simmer, then add your clams. Adjust seasoning.