For me, that was one of the trickiest parts. If you flatten all those flaps out before you adhere your fabric, when you press it up into the roof, it will have a crease, but if you glue the fabric with flaps folded in too tight, you can run into an issue keeping the headliner in the trim (which happened on my passenger side A-Pillar). You have to get it the fabric glued down in roughly the shape when installed to avoid a crease in those spots.
