Preheat oven to 350 degrees F (175 degrees C). Place acorn squash cut side down on a baking sheet.
Bake in the preheated oven until soft and browned, about 30 minutes.
Mix apples, sausage, onion, raisins, poultry seasoning, ginger, cloves, celery seed, salt, and pepper together in a bowl. Spoon sausage mixture into the hollow of the acorn squash; place on the baking sheet.
Bake in the preheated oven until sausage is cooked through and apples are soft, about 30 minutes.