Rinse the fish and pat dry with paper towels. Using a sharp knife, make 4-5 diagonal cut on both sides of each fish. Season fish with salt and then coat entirely with flour, shaking off excess flour.
Heat 1 inch of oil in a large pan over medium high heat. Fry fish, two at a time, until golden brown, about 5-7 minutes. Drain on paper towels and then transfer to a serving plate.
In a small bowl, whisk together ingredients for the sauce. Set aside.
Heat 2 tablespoons olive oil in a skillet over medium high heat. Add ginger and garlic and stir-fry until fragrant. Stir in green onions and then add ketchup and hot chili sauce. Stir until well combined.
Give cornstarch mixture a final stir and then add to the skillet. Stir and cook until sauce thickens, about a minute. Pour over the fried fish. Garnish with chopped green onions.