Preheat the oven to 350°F and grease a 9 x 13-inch baking pan.
Place the cubed bread on a sheet pan and bake for 5 to 10 minutes, until the bread is dried out.
In a large skillet, cook the ground sausage until browned. Transfer the sausage to a plate and set aside.
Melt the butter in the large skillet, then add the onions and celery and cook until the onions have softened, about 4 to 6 minutes. Stir in the apple, garlic, rosemary, thyme, sage, salt, and pepper. Continue to cook for 1 minute. Deglaze the pan with the chicken stock.
In a large mixing bowl, stir together the bread and sausage with the onion mixture. Transfer to the casserole pan and spread evenly.
Bake for 35 to 40 minutes, until golden brown.