In a skillet over medium heat, cook the chopped bacon until crispy. Remove and set aside on paper towels.
In the same skillet, sauté onion and garlic in the bacon grease until soft and fragrant, about 2-3 minutes.
Transfer the sautéed onion and garlic to a slow cooker. Add frozen hash browns, chicken broth, Cajun seasoning, paprika, salt, pepper, and red pepper flakes if using. Stir well.
Cover and cook on low for 6-7 hours or on high for 3-4 hours, until potatoes are tender.
Mash some of the potatoes in the slow cooker with a potato masher for a creamier texture, leaving some chunks.
Stir in cream cheese, cheddar cheese, and heavy cream. Let it cook for another 15-20 minutes on high until everything is melted and creamy.
Serve hot, topped with crispy bacon and green onions.