Whisk the flour and cornstarch in a large bowl. Gradually pour in the room-temperature water while stirring, followed by the kimchi juice, until a smooth batter forms. If the mixture feels too stiff, stir in an extra tablespoon of water at a time.

Fold the chopped kimchi and sliced scallions into the batter. Season with salt, tasting first to see how much salt the kimchi juice has already contributed.

Dissolve the sugar in hot water in a small bowl. Stir in the soy sauce, rice vinegar, sesame oil, sesame seeds, red pepper flakes, and scallions to finish the dipping sauce.

Heat a medium nonstick skillet over medium-high heat with enough neutral oil to coat the bottom. When the oil shimmers, pour in about half a cup of batter and spread it toward the edges until it is roughly half an inch thick.

Fry for 3 to 4 minutes. When the edges look dry and the bottom is deeply golden and crisp, carefully flip the pancake. Cook the second side for another 3 to 4 minutes until it matches the first.

Repeat the frying process with the remaining batter, adding more oil to the pan as needed. Slice into wedges and serve immediately while still hot and crisp with the dipping sauce.