Place the goose in a roasting pan on it's back. Rub the bird all over with the olive oil. Season the goose with the pepper, salt, poultry seasoning, and garlic salt as you please. Next, chop the apple, celery, and onions into chunks. Stuff them into the body cavity of the bird. Put the goose in the oven, uncovered, and roast at 350 degrees for about 25 minutes a pound, or until a meat thermometer reads 165 degrees in the thickest breast meat. When finished, remove stuffing and throw it away. Remove skin and feast!