1Place Reynolds™ Slow Cooker Liners inside a 5- to 6 1/2 -qt slow cooker bowl. Make sure that liner fits snugly against the bottom and sides of bowl and pull the top of the liner over rim of bowl.
2In lined slow cooker, mix potatoes, onion, celery, broth and water.
3Cover; cook on Low heat setting 6 to 8 hours.
4In small bowl, mix flour into milk; stir into potato mixture. Increase heat setting to High. Cover; cook 20 to 30 minutes or until mixture thickens. Stir in cheese until melted. Garnish individual servings with bacon and green onions. Sprinkle with pepper if desired.