Preheat oven to 375°F.
If making your own breadcrumbs, dice half of the bread into ½ inch dice. Place the other half of the bread in a food processor and process into large crumbs. Spread bread over 2 large shallow baking pans and sprinkle with 1 tablespoon Bell’s ground poultry seasoning and bake in upper and lower thirds of oven, stirring occasionally and switching position of pans halfway through baking, until completely dry, about 25 minutes. Transfer bread to a large bowl.
On a sheet tray, mix butternut squash with olive oil, allspice, nutmeg, and salt and pepper. Roast until nice and crisp, around 10-15 minutes.
Melt 6 tablespoons butter in a large skillet over medium heat. When butter foams, add the celery, onion, apples, bay, herbs, and salt and pepper, and cook to soften 10-12 minutes. Add cubed bread and roasted squash, then season with 1 tablespoon Bell’s and moisten with stock; stir to absorb.