Place apples in slow cooker. Combine sugar, cinnamon, cloves and salt; pour over apples and mix well. Cover and cook on high for 1 hour. Reduce heat to low; cover and cook for 9 to 11 hours or until thickened and dark brown, stirring occasionally (stir more frequently as it thickens to prevent sticking). Uncover and cook on low 1 hour longer. If desired, stir with a wire whisk until smooth. Spoon into freezer containers, leaving 1/2 -inch head space. Cover and refrigerate or freeze. Makes 4 pints.