Pour oil a quarter-inch deep in the pan or pans and turn heat to medium-high. When the oil shimmers, drop in a potato shred. If it bubbles up immediately, the oil is hot enough. Use a quarter-cup measure to scoop potato batter, packing it in with your fingers, then place each scoop gently in the oil. Flatten with the bottom of the cup to about a half-inch thick. Repeat, leaving space between patties in the pan.