Want to change up your stuffing this year? Add bacon.
Preheat the oven to 325º. Grease a 9-by-13-inch baking dish.
Divide the bread pieces between 2 large rimmed baking sheets, arranging in a single layer. Bake, stirring occasionally, until the bread is dry and crisp, 25 to 30 minutes. Let cool; transfer to a very large bowl. (Leave the oven on.)
In a large skillet, cook the bacon over medium-high heat, stirring occasionally, until crisp, 15 to 20 minutes. Using a slotted spoon, transfer the bacon to paper towels. Pour off all but 2 tbsp. of the bacon grease from the skillet (reserve the remaining grease for another use).
Add the butter to the skillet with the bacon grease. Heat over medium-high until the butter melts. Add the leeks, chopped celery, rosemary, oregano, and thyme; season with salt and pepper. Cook, stirring often, until the vegetables are tender, 6 to 8 minutes.
Add the vegetables from the skillet, the celery leaves, parsley, and bacon to the bread cubes; toss to combine. Stir in the stock, then the eggs. Transfer the mixture to the baking dish.
Bake until the stuffing is cooked through and golden brown on top, about 1 hour.