In a large dutch oven, cook bacon over medium heat.
Once bacon is crispy, remove to a paper towel lined plate to drain excess grease. Do not drain grease from the dutch oven.
Melt butter in the dutch oven with the bacon grease.
Add celery, onions, and garlic. Sauté the vegetables until tender.
Dust the vegetables with flour and stir to coat and cook for 2-3 minutes.
Pour the chicken broth into the dutch oven and stir, scraping the bottom to remove any stuck flour or brown bits from the vegetables.
Add the bay leaf, cayenne pepper, black pepper, and sea salt. Stir to combine and simmer for about 5 minutes to thicken the base.
Using a small strainer, pour the clam juice from the cans of chopped clams to the dutch oven. Reserve the clams to be added later.
Add the diced potatoes and simmer for 15 minutes, or until the potatoes are tender.
Once the potatoes are tender, add the heavy cream, milk, and clams.
Turn off the heat and stir to combine. If the chowder is very thick at this point, more milk can be added to thin the base.
Stir in half of the chopped crispy bacon to the chowder. The other half of the bacon will be for garnish.
Serve immediately garnished with chopped bacon and green onions.