Short answer, not sure you can. A lot of the aftermarket flaps use the trim bolts for the side skirt at the back, but it also means securing it higher up too.
Rallyflapz have a bracket that attaches nicely to the trim to secure them - it's the best way i've seen after fitting a couple
Rallyflapz have a bracket that attaches nicely to the trim to secure them - it's the best way i've seen after fitting a couple