Preheat oven to 300°F. Spread bread cubes out on two large rimmed baking sheets and bake until dried but not browned, about 15 minutes. Transfer to a large bowl.
In a large skillet, heat oil over medium-high heat. Remove the sausage from the casings, and add it to the skillet to cook, breaking up chunks with a spoon, until browned, about 6 minutes.
Add apples, celery, onion and butter and cook, stirring occasionally, until apple and vegetables are softened, 8 to 10 minutes more. Add to toasted bread. Stir in broth, poultry seasoning, sage, salt and pepper.
Add stuffing to a freezer-safe greased 9x13 foil pan. Place in the freezer (for up to four weeks). 1-3 days before, remove the stuffing from the freezer. Drizzle a ½ cup additional chicken stock over the top to moisten the stuffing. Heat oven to 350°F and bake until lightly browned and crisp on top, 50 to 60 minutes. This stuffing can also be stuffed in your turkey, just be sure that the stuffing has cooled before proceeding.
Garnish with fresh sage leaves.
Recipe by MomAdvice at http://momadvice.com/blog/2013/11/make-ahead-apple-sausage-and-sage-sourdough-stuffing