Transfer grated onion and potato into a clean dry dishtowel and squeeze all the liquid from the vegetables. Place bundle in a colander placed over the sink, and let stand 15 minutes. At the end of that time, squeeze as much remaining liquid from the vegetables as possible. Note: The key to crisp latkes is to remove as much water from the vegetables as possible.
In a large mixing bowl, whisk together the flour, eggs, salt and pepper. Stir in potato and onion mixture and stir until combined and evenly coated.
Heat 1/4-inch of vegetable oil in a medium or large skillet over medium heat. Drop potato mixture by heaping tablespoon into the heated oil, flattening the mound with the back of a spoon. Cook until edges are golden, 2 to 3 minutes, and turn. Cook an additional 1 to 2 minutes or until golden and potatoes are tender. Transfer cooked latke onto paper towel to drain. Repeat with remaining potato mixture. Makes approximately 2 dozen latkes.
Keep warm in a preheated 200 F oven. To re-warm leftover latkes, place in a single layer on a rimmed baking sheet. Heat in a 400 F oven until hot and crisp, 7 to 8 minutes.