Flatfish are a saltwater group of fish that includes flounder, sole and halibut. The body is thin and oval shaped, with the back on the top side and the belly on the underside. Flatfish have the unusual characteristic of having both eyes together on the top side of their head. A continuous line of fin follows around both edges of the fish's body between the head and tail. Two pectoral fins are on the bottom of the fish at the gill opening. Gutting a flatfish is a different procedure than for a round shaped fish.
Lay the fish on its back so the belly is up and the head is to your right.
Start a cut through the skin at the edge fin to the left side of the lower little pectoral fin by the gill opening. Cut up the fish's body to the upper pectoral fin, keeping the fin to the right side of your knife.
Make a second cut following the intestinal cavity opening along the edge fin. Cut toward the tail and stop the cut at the end of the cavity. The length of this cut will be dependent on the size of the fish and length of the cavity.
Lift the triangle-shaped flap of skin and scoop out the intestines with your fingers.
Cut off the head by cutting completely through the fish following the outside curve of the gill openings, leaving the pectoral fins with the removed head portion.
Most flatfish are filleted. If the fish is to be filleted, then it is not necessary to gut the fish. Some people leave the head on the fish when cooking it whole. If the head is to be left on, the gills need to be removed. This can be done by using a pair of utility scissors and clipping through the upper and lower ends of the gills where they attach to the gill opening.
Cut away from yourself, not toward you. A slip of the knife can bring the blade into you if you are cutting toward you.