The direction of the slots on the outside of the rotor do not dictate whether the rotor is a left or a right. For rotors
with slots machined in the same direction as the internal cooling vanes, the slots should lean toward the back of the
car. For rotors with slots machined in the opposite direction as the internal cooling vanes, the slots should lean
toward the front of the car. Bottom line - don't use the slots to decide which side to mount the rotor. Pay attention
to the internal cooling vanes.
For slotted rotors with straight internal cooling vanes, the direction of the slots is totally up to you and what you think
looks best. In this case, there is no wrong answer.