In fact, there are various methods for your reference if you need to stack two circuit board. For example,
a:BTB(circuit board to circuit board )
b.BTW(circuit board to wire)
c.WTW(wire to wire or FPC to FPC)
d.Welding the two circuit boards directly
The same, in order to space apart two circuit boards, you can also consider it as the above methods shows.
Sure, if you still have other questions, please feel free to ask Shenzhen Grande.