2. Preheat the oven to 375 degrees. While it's warming up, heat the oil in a deep-fryer or heavy pot to 350 degrees. Rinse the walleye fillets in cold water, then pat dry with paper towels. Spread the remaining flour on a plate and dredge the fillets in the flour, shaking off any excess. When the oil is ready, dip the floured fillets in the batter one at a time, fully coating it so that the batter is thick and drippy. Add to the oil, and continue with the remaining fillets. Fry 7 to 10 minutes, or until the fish is cooked through and golden brown.