Preheat the oven to 250 degrees F.
Cut the bread into 1/2" to 3/4" pieces and lay them in a single layer on baking sheets.
Bake in the preheated oven for about 1 hour, tossing a few times to make sure all sides are dry. Once dried, remove from the oven and transfer to a large bowl. Set aside while you make the rest of the stuffing.
Increase oven temperature to 350 degrees F.
Put butter to a large pot over medium heat and melt. Add the celery and onions and cook, stirring frequently, until tender and translucent—about 8 minutes.
Add the sausage and use the bottom of the spoon to break the sausage up into small chunks. Cook the mixture until the sausage is no longer pink, then add the diced apples and cook for an additional minute. Finally, add the poultry seasoning, minced parsley, thyme, sage, salt, pepper, and chicken broth.
Stir, then pour over the dry bread. Gently fold together—it should be moist but with no standing liquid. If it seems a little dry, add an additional 1/2 cup of chicken broth.
Spray a 9" x 13" baking dish with nonstick cooking spray, then spread the bread mixture evenly over the bottom.
Bake in the preheated oven for 45-60 minutes, stirring gently every 15 minutes, or until the top is lightly brown.
Remove from the oven and serve warm. Enjoy!