Its tough to say if a flat bottom wing flies with 0 angle of attack.. This may depend on where the balance point is.. But on a flat bottom wing, you are getting the majority of the lift from the shape of the wing, or it's camber.. this is why a flat bottom aircraft flies like c@@@ when it is upside down.. You need a tremendous amount of AoA in order to overcome the fact that the wing is now producing lift in the direction of terra firma..