Flank hernias are uncommon hernias involving the abdominal oblique muscles. Large incisional flank hernias are complex to repair, given the proximity of bony prominences, major neurovascular structures and lack of available tissue for primary closure. We review the literature and report a case of a large 22×10 cm incisional flank hernia containing a transverse colon, small intestine, omentum and previous polypropylene mesh. The patient underwent an elective open hernia repair using a novel sandwich (sublay fixed onto onlay) mesh technique, with an excellent postoperative outcome.