Spine and flo

Is the spine finder just a quick way to start with the flo. Took my shafts off since not golfing at the moment. Found the spine,a hump i would call it and marked it ai 12 oclock.I assume that would be the stiffest part 12/6. Then proceed to flo moving that line to 3 o'clock since I am a lefty. The NBP would be on the 3/9. I might not understand it completely since if the spine (hump) is on top, the shaft wants to to right or left. Would the right or left be the NBP.Was thinking that if the spine is on top and install it that way in my iron it would be in it's natural bending motion.When I flo them except for one that flows perfectly in that position all others were perfectly flowed at the 3 o'clock.
Thanks