Preheat the oven to 425°F (220°C). Prepare a large baking sheet by lining it with parchment or applying a light coat of cooking spray. Rinse and pat dry the potatoes, then cut them into uniform ¼-inch rounds. Peeling is unnecessary.
Place the potato slices in a single layer on the prepared sheet. Lightly brush each side with olive oil, then season evenly with salt and black pepper. Bake for 15 to 20 minutes, turning the slices over at the halfway point, until both sides are golden and tender when pierced.
Once baked, sprinkle the shredded cheddar cheese generously across the top of each potato round. Distribute the crumbled bacon over the cheese. Return the tray to the oven for an additional 2 to 3 minutes, or just until the cheese is fully melted and bubbling.
Carefully remove the tray from the oven and let the rounds rest briefly. Top each one with a small spoonful of sour cream and garnish with freshly sliced green onions. Serve while warm.