Spray 4- to 5-quart slow cooker with cooking spray. Place turkey in slow cooker; sprinkle with garlic-pepper blend and salt. Stir in remaining ingredients except half-and-half and cornstarch.
Cover; cook on Low heat setting 6 to 8 hours.
In small bowl, mix half-and-half and cornstarch until smooth; gradually stir into chowder until blended. Increase heat setting to High. Cover; cook about 20 minutes longer, stirring occasionally, until thickened.