Heat the oven to 350°F. Spread the bread cubes on a large baking sheet and dry in the oven for 10 minutes, stirring once; transfer to a large bowl.
Use 1 tablespoon butter to grease a 9-by-13-inch baking dish. Melt the other 5 tablespoons in a skillet and cook onion and celery for 8 to 10 minutes until softened; stir in sage, thyme, salt and pepper.
Toss the vegetables with the bread. Whisk broth and eggs together, pour over the bowl and fold gently until evenly moistened; let stand for 5 minutes.
Spoon loosely into the baking dish without packing down. Cover with foil and bake for 25 minutes.
Uncover and bake for 15 to 20 minutes until the top is golden and the center reaches 165°F. Let stand for 10 minutes before serving.