Asked my teacher about looking after reeds and placing them in the reed guard.
He said, in his opinion, it doesn't matter about keeping them flat in the reed guard. As soon as you suck them before playing, they will striaghten out.
Also he leaves his reed on the mouthpiece on the sax, but with the guard on. It reduces the risk of damaging the reed each time you put it on and take it off the mouthpiece.