Remove scales and slime by placing the mackerel with its head to the left and belly facing you. Use a knife to scrape from tail to head on both sides.

Cut off the head by placing the mackerel with its head to the left and belly facing you. Insert the knife under the pectoral fin and cut until you hit the backbone. Flip and repeat on the other side.

Remove the internal organs by cutting from the head side to the anus along the belly. Scoop out the organs.

Open the belly cut and scrape out the blood membrane around the belly bones using a spoon. Wash thoroughly and pat dry with kitchen paper.

Place the mackerel diagonally with the head to the upper right and belly facing you. Slide the knife along the backbone from head to tail to separate the top fillet.