In a small bowl, combine thawed orange juice concentrate, marjoram, garlic powder and nutmeg. Dip each chicken breast in juice mixture to coat, then add to crock pot. Once all breasts are done, pour remaining mixture over top.
Cover and cook on low for 7-9 hours or on high for 4-5 hours.
Ten minutes before serving remove chicken, then pour sauce into medium saucepan. In small bowl, combine cornstarch and water until smooth, then pour into saucepan. Heat over medium heat, stirring until sauce thickens. Serve sauce with chicken and rice or pasta.