Preheat your oven to 250°F. Spread the bread cubes in a single layer on two large baking sheets and bake for 45-50 minutes to dry them out, stirring occasionally, until they are crisp and feel hard to the touch.
Melt the butter in a large skillet or Dutch oven over medium heat. Add the chopped onion and celery and cook for 8-10 minutes, stirring occasionally, until the vegetables are softened and translucent. Add the minced garlic and cook for 1 more minute until fragrant.
In a very large mixing bowl, combine the dried bread cubes, cooked vegetable mixture, parsley, sage, thyme, rosemary, salt, and pepper. Gently toss until everything is evenly distributed.
Pour the chicken broth and beaten eggs over the bread mixture. Using a large spoon or your hands, gently toss until all of the bread cubes are moistened. The mixture should hold together when pressed; if it seems dry, add more broth 1/4 cup at a time.
Increase the oven temperature to 350°F. Transfer the stuffing mixture to a greased 9x13-inch baking dish, cover tightly with foil, and bake for 30 minutes.
Remove the foil and continue baking for another 20-30 minutes, until the top is golden brown and crisp.