Preheat oven to 400 F.
Bring a medium pot of water to boil.
Wash and scrub the potatoes very well on the outside. Slice thinly using a mandolin, or if you don't have one cut them very thinly, about 1/8 of an inch thick. Rinse and set aside.
Drop the potatoes in the boiling water. Set your timer to 2 minutes. DO NOT boil for more than that.
Transfer them gently into a strainer and run the cold water on them to stop them from steaming more. Turn off the water and let all the water drain off the potatoes.
Line a large sheet pan with, or use two medium sized ones if you want, with parchment paper.
Arrange the potato slices in a single layer, without overlapping any. Pat down the potatoes very gently with some paper towel to remove any remaining moisture.
Spray the potatoes with olive oil spray and then add some salt and everything but bagel seasoning to taste and preference. Flip them over and repeat the same steps for the second side.
Bake in the preheated oven for 20 -25 minutes, more or less until the potatoes start to get brown and crispy. You can also use a nonstick wired rack instead of parchment paper.
Remove from the oven and allow them to cool up a little before serving. Serve with your favorite dip or sauce.