Oil vent trap

I will put the gopro in there.

vent line is facing the rear of aircaraft. what direction should face?

Where does the knotch go exactly

The location of the notch and direction of the vent line is determined empirically.
The correct answer is, " Whatever works for you".

Before you change anything, determine where the actual problem lies.
Otherwise, you could end up chasing your tail.
If you find that you blow oil at Idle on a cold engine, The problem is in the Oil tank, not the Vent Hose.