Place the sanma with its head to the left. Using a knife, scrape off the scales from the tail towards the head.

Position the sanma with its head to the left and belly facing you. Cut straight through behind the pectoral fin to remove the head.

Turn the fish so the head is on the right and belly facing you. Hold the back with your left hand and make an incision from the center of the belly to the anus.

Remove the internal organs and use the knife tip to cut into the membrane of the bloodline.

Scrape off the bloodline and wash the fish. Pat dry with kitchen paper.

With the head to the right and belly facing you, hold the back with your left hand. Make a cut along the backbone from the head to the tail, separating the flesh at the tail end.

Flip the fish over with the head to the right and dorsal fin facing you. Cut along the backbone from the dorsal side to fillet the other side.