Trim ends from green onions and cut the roots off; wash 2 to 3 times in cold water and cut into 8 inches from white part. Drain green onions in a colander.
Heat about 1 teaspoon vegetable oil in a large skillet over medium heat. Place 1 green onion in 1 direction and 1 in the other direction, repeating until 8 are used for each serving batch.
Mix flour, water, and salt together in a bowl until batter is smooth. Pour 1/4 of the batter over the green onions in the skillet; top with 1/4 of the seafood mix. Cook until seafood is cooked through and pancake is lightly browned on the bottom, about 10 minutes.
Whisk eggs together in a bowl. Ladle 1/4 of the eggs over pancake; cook until mostly cooked, about 5 minutes. Flip pancake using 1 or 2 spatulas and cook for 10 minutes more. Repeat with remaining oil, green onions, batter, and egg.
Whisk soy sauce, Korean red pepper powder, vinegar, sesame oil, sesame seeds, and black pepper together in a bowl; serve alongside pancakes for dipping.