April 19, 2018 HOW TO FILLET MACKEREL by Cafe St Honoré in Recipes Neil takes us through a step-by-step guide of how to fillet mackerel. In just four easy steps, he makes it look so simple! STEP ONE Remove the head and guts. STEP TWO Insert knife just above back bone and remove the fillet. STEP THEE Using a filleting knife, remove the belly bones. STEP FOUR Using the same sharp knife, insert it either side of the central pin bone line and remove all bones in one. VOILA! The final boneless, skin-on fillet is ready for pickling, frying or grilling.