How are wearing the watch?
Like a normal person with the face on top of the wrist, or like a psychopath and the face on the underside of the wrist?
In which direction?
Face up so I can align it to the sun.
Top of the wrist.
I can do either position. What would be more recommend?
Personally I would go for red line.
but of you want to do testing, maybe 3d print a test model, like the FlexDF2 here
or just cut out a similar sized/shaped model in thin plastic, and stick it down on your wrist in each orientation to find a comfortable/suitable position.
Ideally you want the orientation to be one that will flex the least