Combine all the soup ingredients in a slow cooker and cook on high for 3-4 hours, until the beans are tender.. Remove rosemary stems (the leaves will have mostly fallen off into the soup and that’s okay.) Using an immersion blender, very roughly purée the soup just enough to thicken it. There should still be plenty of texture and big pieces of carrots and whole beans. Alternatively, purée half the soup in a blender and return it to the pan. Add more salt to taste if needed.