Cook bacon in a skillet until crisp. Remove bacon from pan and reserve about 1 tsp of bacon grease in the pan. Add in onion and saute for another 5 minutes or until tender. Crumble the bacon and set aside.
Combine broth, salt, onion and green beans in a slow cooker. Cover and cook on low heat for 8 hours or until beans are tender. Transfer beans to a serving dish with a slotted spoon. Sprinkle with the crumbled bacon and serve hot.