Preheat the oven to 400 degrees. Line a rimmed baking sheet with foil and coat with nonstick cooking spray (this makes clean-up really easy!) Lay the bacon strips flat, making sure pieces do not overlap. Bake until crisp and browned, 15 to 18 minutes, or desired doneness. Using tongs, transfer strips to a paper towel to drain, then chop into pieces.
In the meantime, place the flatbreads on a baking sheet and sprinkle the cheese evenly among them. Warm them in the oven for 8-10 minutes until the cheese has melted.
Distribute the lettuce, cucumber, tomato, avocado, scallions, and bacon pieces onto each flatbread and drizzle with 2 tablespoons of the Ranch dressing.