I've never in my life lined up any arrow on the pressure plate to anything else.
I'd love to know what that would do anyway.
How do you know for sure that it's slipping? You say that after a while it goes away? It would be normal for the clutch to slip after extended periods of riding, not the other way around.
You installed a new clutch, but what about your basket, inner hub and pressure plate? Are they worn? If so, a new clutch won't fix the real issue.