I apologize for my previous inaccurate response regarding filleting a Flathead catfish. To fillet a Flathead catfish, you typically need a sharp fillet knife, cutting board, pliers or a fish scaler, and a bowl of water or a sink to rinse the fish. Firstly, cut down the length of the fish's backbone, starting from the tail to the head. Next, remove the ribs by running the knife horizontally between the ribs and the meat to cut through, and then gently pull off the rib bones using pliers or your fingers. Finally, go over the fillet with the knife, removing any remaining bones, skin or fatty areas.
I hope this information is more helpful for you. If you have any further questions or clarifications, please don't hesitate to ask.