Slice potatoes thinly, about 1/8 - 1/4 inch thick.
Spray 7 x 3" cake pan with cooking spray.
Layer half of the potatoes into pan and sprinkle with half of salt, pepper, garlic powder, oregano and minced onion. Cover with half of cheese and half of bacon.
Repeat with remaining potatoes, seasoning, bacon and cheese. Save a little bacon to garnish the top with. Pour half and half over potatoes.
Add 1 1/2 cups of water into Instant Pot. Place cake pan on the rack that comes with the Instant Pot and place potatoes into Instant Pot.
Put lid on Instant Pot and set to manual, high pressure for 25-30 minutes depending on how thick you cut your potatoes.
Be sure knob is set to the sealing position. When cycle ends, do a quick release and open lid. If potatoes are not done to your liking put lid back on, reset for another 2-5 minutes.
Garnish with Parmesan cheese, remaining bacon and green onion.