Open the bag of frozen diced hash browns and dump them into the insert of your slow cooker.
Trim the root ends from your bunch of green onions and discard them. Slice the green onions into about one inch pieces. Soak them in cold water for a few minutes, rinse and drain. Reserve the green tops for topping your soup. Add the white and light green parts of the green onions to your potatoes in the Crockpot.
Season the potatoes and green onions with the salt and pepper.
Microwave the butter until melted. Whisk in the flour and microwave for one minute. Whisk again and repeat two more times, microwaving the flour and butter together to form a bubbly roux (a total of three minutes).
Whisk the chicken broth into the roux until smooth. Then whisk in the fat free half and half until smooth.
Pour the thickened chicken broth mixture into the slow cooker insert with the seasoned potatoes and green onions.
Cook on LOW power for about 6 hours, or HIGH power for about 4 hours, or until the potatoes are completely tender.
Stir in one cup of shredded extra sharp cheddar cheese and one cup of sour cream into the cooked potato soup.
Blend the soup with an immersion blender until smooth. Continue to slow cook the soup until it is hot.
Serve the soup topped with cooked bacon, chopped green onions, more sour cream and shredded cheddar cheese.