It's not the slots but the vanes inside the rotor that determine direction. If the the rotors you buy have curved vanes then the curve should spiral out (or curve to the rear) in the direction of rotation, if the vanes are straight, then is doesn't matter and becomes your preference.
__________________ 2011 SS Conv. ,M6, Black - stock
2000 SS Conv., M6, Onyx,
TTS LTs, AFR 205s milled, 220/224 581 581 114, Cometic .040, Z6 Int. & clutch, 3.73s,ASP, 180 stat, Rapid tune, LCAs, Brkts, SLP Level II, Hurst Billet+.
Appearance: Mark's decals, black calipers, AR TTIIs (Gunmetal Spokes).