In a 5 quart crock pot (or larger), add shredded potatoes, chicken broth, pepper, and red pepper flakes. Set cooker to low and cook for 6-8 hours.In a medium bowl, whisk together milk, flour, sour cream, and cheddar cheese. Add mixture to crock pot and stir in any additional veggies of your choice (optional). Cover and let cook for another 30 minutes.Stir soup before serving. Garnish with more cheese, a dollop of sour cream, and chopped chives.