Place the fish on the counter or other flat clean surface. Keep a bucket nearby to collect all the icky, slimy parts for the sleens.
Working from tail to head, against the direction in which the scales lie, scrape the back of a knife blade along the skin to remove the scales. Save the scales, if pretty, for use in making jewelry or decorating pottery later. The fish can be rinsed in a basin of cool water to remove any scales that may stick.
Cut off the fins behind the head, ones on the belly, and any other fins including the tail. Hook your finger through the gills and either pull or cut them out. Chop off the head next and make a cut down the belly of the fish. Stick your hand inside and scoop out all the guts and entrails. Save them for feeding the sleens.
To fillet the fish, cut down the back of the fish from the tail to the head. Then cut down to the backbone. Angle the knife to cut away the flesh from the backbone, allowing the knife to run over the rib bones. Lift off the side piece, freeing the fillet at the tail. Turn the fish over, and cut the fillet from the other side. The fillets need to be wrapped and stored in the cooling shed.
If you wish to skin the fillet, lay it skin-side down on the counter. Hold the tail end with your fingers, and cut through the flesh away from it by running the knife forward while holding the free end of the skin firmly between your fingers.
Next, you need to dry and prepare the scales for use. Sprinkle alum over the scales to keep them from becoming brittle. If they are large, the scales must be weighted while they dry to prevent them from curling up.
Once they are dry, bosk glue can be used to attach the scales to pottery or other hard surface, painting should be done after they are glued on, similar to urth plastic ornaments or conchos. The scales can also be used to make binas.