Yeah, so it's important that lams are consistant in thickness from side to side so that limb twist isn't built in... and accurate in taper so there are no flats, hinges, or bad glue lines built in.
In tri-lams, the prep work is, or should be, largely where the quality of the bow is determined. If everything is done accurately, well proportioned, well designed and coordinated... the work AFTER the glue up is a cakewalk.