In a saucepan add oil, black bean, chili flakes, ginger and garlic and lightly sauté. Add in sugar, oyster sauce, clam juice and cornstarch roux to lightly thicken and keep warm.
Take the whole catfish and clean inside and outside and with a chef knife make 3 slice along the side of the catfish about 2” apart and season with salt the inside and outside and cover the catfish with cornstarch and pat off extras cornstarch.
In a wok halfway fill with oil over a high heat to 350° and place the catfish head first and lower catfish into the hot oil and deep fry to a golden brown and with a wok spatula of hot oil pour over the catfish. Place the cooked catfish onto a large serving platter and pour the spicy black bean sauce over the catfish.