Explore Leiths Diploma Open House – 5th June 2024


How To Fillet a Flat Fish

This method removes 4 fillets from a flat fish. Fishmongers will often remove a whole side, so 2 double fillets from each flat fish. What is important is that you develop a method of filleting that you are comfortable with, that you use your knife safely and that you waste as little fish as possible. It is essential to use a very sharp knife, preferably with a long flexible blade. First rinse the fish under cold water and dry with kitchen paper. Fish have a natural slime and rinsing it off makes it easier to handle.

1. Cutting along the natural line down the middle of the fish from below the head to the tail.

2. Cutting across the top of the tail.

3. Cutting beneath the gill and head.

4. Carefully cutting the fillet away from the bone.

5. Lifting the fillet as it is released.

6. Gripping the edge of the skin and pulling the fillet away from the body.

7. Inserting the knife on the right side of the back bone before starting to remove the second fillet.

8. Repeating the filleting process on the pale underside to remove the other 2 fillets.

9. The 4 fish fillets removed from the frame, ready to skin if required.


  1. Place the fish on a board, tail end towards you and darker side uppermost. Using a fish filleting knife, make an incision along the natural line running down the middle of the fish, from behind the head down to the tail.
  2. Make a small cut across the top of the tail.
  3. Make a cut from behind the head down to the edge of the fish behind the gill and head on both sides.
  4. Release a little of one of the fillets from the back bone, the full length of the fish. Then, using the flexibility and length of a fish filleting knife and long strokes, carefully release the fillet away from the skeleton. Try to keep the knife as flat against the bone as possible. You should hear a rasping sound as the knife blade works its way across the bones.
  5. As the knife approaches the edge, lift up the fillet to make it easier to see what you are doing.
  6. When you reach the frill, either grip the edge of the skin of the fillet and pull the fillet firmly away from the body, taking care not to damage the flesh, or cut the fillet away from the frill and main body of the fish.
  7. Repeat with the remaining top fillet. You need to ensure the knife blade is on the right side of the little vertical back bone before starting to remove the fillet.
  8. Turn the fish over and repeat the process on the pale underside. The skin here is a little tougher.
  9. Once you have removed all 4 fillets, put them aside ready to skin or cook with the skin on. Remove the head from the frame, bend the frame to break the bone and cut through the breaks, then rinse the bones and use for stock, or freeze for later use.

Note Now scrape the board to get rid of any loose bits of fish and rinse well under cold water, then wash well under hot water and detergent. Dry well.