Preheat the oven to 350°F (175°C) and grease a 9x13-inch baking dish.

Cut 6 cups of day-old bread into 1-inch cubes and place them in a large mixing bowl.

Melt 1/4 cup of the unsalted butter in a skillet over medium heat, then add the chopped celery and onion and sauté for 5-7 minutes until softened.

Add the chopped oysters to the mixing bowl with the bread cubes and sautéed vegetables.

Stir in 1 teaspoon dried thyme, 1 teaspoon dried sage, and season with salt and pepper to taste.

Pour in 2 cups chicken or vegetable broth, stirring gently to combine and ensure even moisture distribution.

Transfer the mixture to the prepared baking dish and drizzle the remaining 1/4 cup melted butter on top.

Cover the dish with foil and bake for 30 minutes, then remove the foil and bake for an additional 15 minutes until golden brown.

Let the dressing rest for 5 minutes before serving.