Place potatoes and leeks in slow cooker. Sprinkle flour over and toss until well-coated. Add the chicken stock and stir, then add the dill and the chopped bacon. Mix well. Cover and cook on low for 7 to 8 hours or until the potatoes are tender.
In a blender or food processor, puree the soup until creamy (you can puree the whole pot or just some of it if you prefer a chunkier soup). Add salt and pepper to taste (I find a teaspoon or two of salt really helps boost the flavor).
Stir in half and half and cheese (if using), then cover and heat an additional 15 minutes.