Cook the Bacon: Brown the bacon in a Dutch oven or large saucepan over medium heat. Remove the bacon with a slotted spoon and drain it on paper towels; then crumble and set it aside.
Sauté the Onion and Make the Roux: Remove all but 2 tablespoons of drippings from the pan and add the chopped yellow onion. Sauté for 3 to 4 minutes, or until translucent. Add the flour and cook, stirring, for 2 minutes.
Simmer the Base: Add the clam juice, undrained minced clams, diced potatoes, water, and 1 teaspoon of kosher salt to the roux. Bring to a boil, then reduce the heat to low and simmer until the potatoes are tender.
Add the Dairy and Corn: Stir in the butter, evaporated milk, green onions, cream-style corn, and freshly ground black pepper. Taste the chowder at this stage and add more salt if needed, as the dairy and corn will soften the flavors.
Finish and Serve: Sprinkle crumbled bacon over each serving.
Notes
If you prefer a thicker chowder, mix 2 tablespoons of flour with 1 tablespoon of cold water to make a smooth paste. Stir it into the soup and cook until thickened.