Normally, from a 4 lb turbot, you will get 1.5 lb of fish fillets.
Use a sharp knife to cut around the bones of the turbot.
Holding the knife at an angle, separate the fillet by running the knife between the flesh and the bones.
Continue along the backbone to the end of the tail.
Repeat steps 2 and 3 for the other fillets.
Clean up the fillets by removing any membranes and the parts with blood. Also clean up the edges of the fillets, removing any small bones that were left.
Once the turbot has been filleted, cook it as you desire.