Place the bacon in a large, deep skillet, and cook over medium-high heat, turning occasionally, until evenly browned, about 10 minutes. Remove the bacon slices to cool. Whisk the butter, flour, and salt into the drippings in the same pan. Stir in the cabbage, and cook, stirring occasionally, over medium heat until cabbage is tender, about 15 minutes. Crumble the bacon; stir the bacon pieces and sour cream into the cabbage mixture.