Combine flour and garlic dressing mix in a large resealable plastic bag. Set aside.
Rinse and dry potatoes. Using a mandoline slicer, cut thinly into round disks. Starting with sweet potatoes, add about half of the slices to the seasoned flour. Shake in bag. Arrange on a sheet pan and repeat with remaining potatoes. Chill seasoned potatoes for about 20 minutes.
Pour oil into a large, heavy-bottomed Dutch oven until it is a little less than halfway up the sides of the pot. Heat oil to 375 degrees F.
In small batches, fry potatoes until crisp. Drain on paper towels season with salt and pepper, to taste. Repeat with the rest of the potato chips.