Preheat oven to 400 degrees. Line a baking sheet with aluminum foil.
Spread bacon in a single layer onto the prepared baking sheet. Place into oven and bake until brown and crispy, about 12-14 minutes. Let cool before crumbling; set aside.
Line a slow cooker with aluminum foil, leaving enough to overhang to wrap the potatoes on top, and coat with nonstick spray. Place a layer of potatoes evenly into the slow cooker. Top with cheese, Ranch Seasoning and bacon, repeating 2 more times and reserving 1/2 cup cheese.
Cover potatoes with aluminum foil and cook on low heat for 7-8 hours or high heat for 3-4 hours. Sprinkle with remaining 1/2 cup cheese. Cover and cook until melted, about 1-2 minutes.