Cook veggies in broth and seasoning. Put the hashbrowns, chicken stock, salt, black pepper, and granulated garlic in a 6-quart or larger slow cooker, and mix them well. Cook on HIGH for 2 hours or LOW for 4 hours until the potatoes are soft.
Prepare the roux. When the potatoes are almost ready, melt butter in a skillet or saucepan over medium heat. Slowly add the flour while whisking until smooth. Cook for 1-2 minutes, stirring all the time, to get rid of the flour taste.
Add dairy. Slowly add the half & half while stirring. Turn up the heat to medium-high and keep stirring until the mixture thickens. Take it off the heat and mix in the sour cream until it's all combined. (Optional: If you want the soup smoother, you can use a hand blender or pour it into a regular blender and blend until it's smooth.)
Combine and finish cooking. Add the half & half mixture to the slow cooker with the potatoes. Mix well. Cover and cook on HIGH for another 30 minutes until the flavors mix and the soup thickens.
Garnish. Serve the soup hot, garnished with shredded Colby jack cheese, crumbled bacon, and sliced green onions.