Preheat the oven to 375 degrees F. Place two roasting sheet trays in the oven to heat up (hot trays help keep the potatoes from sticking).
Wash and lightly scrub the potatoes to remove any dirt or tough skin. Using a sharp knife or a mandolin, slice the potatoes lengthwise into 1/4-inch planks. Place in a large bowl or pot of water and rinse to remove excess starch. Drain well and pat dry.
In a large bowl, combine the olive oil, minced garlic and some salt and pepper. Add the potato planks and toss to coat everything evenly. Remove the hot trays from the oven and set out the planks on the trays in a single even layer. Lightly sprinkle the paprika on the potatoes then place the trays back in the oven and roast until golden and crispy, 20 to 25 minutes, flipping halfway. When done, use a fish spatula to remove from the trays. Season with salt and serve with ketchup.