Preheat oven to 425F. Line a baking sheet with aluminum foil.
Carefully slice potatoes to a 1/4-inch thickness.
Pat potatoes dry with a towel and add to a bowl. Toss with oil.
Place potatoes in a single layer on the baking sheet and sprinkle with salt.
Bake at 425F for 20 minutes, flip over and bake another 15-20 minutes, until potatoes are tender and lightly browned.
Either transfer potatoes to a oven safe plate or cast iron skillet. Place half of the potatoes on the plate, cover with half of the cheese and bacon. Repeat again.
Bake an additional 5-10 minutes, until cheese is completely melted.
Top with sour cream and chopped green onion to serve.