In a 6 quart oval slow cooker or similar size crockpot, add hash brown potatoes, carrots, onion, celery and garlic. Stir together.
Add chicken stock, butter, garlic salt, black pepper, onion powder, paprika and Italian seasoning. Stir together to combine. Cover tightly, cook on low for 4 hours.
After 4 hours, check potatoes for doneness they should be fork tender. Use a slotted spoon to remove about ½ cup of potatoes. Mashed with a fork or potato masher, then return to slow cooker. Increase slow cooker to high.
In the same bowl, whisk together half and half, sour cream and all purpose flour until smooth and no lumps remain. Whisk into soup. Add ham and shredded cheese, mix well.
Cover and cook for 45-60 minutes, or just until thickened. Uncover, mix in fresh parsley. Let stand for 5 minutes.
Serve immediately topped with bacon, cheese and parsley or green onion.