U just have to adapt.one formation can have many variations.if ur playing against 3-5-2 flat then u have to put DMC in central midfield with blue arrows so that u have 5 in central midfield which forms a 3-5-1-1 formation which is useful for maintaining possession in the game.DMC is not required to counter 3-5-2 flat as that formation does not have AMC to counter against.using an AMC will be useful as in 3-5-2 flat opposition does not have DMC.in this way there will be a strong link between midfield and attack.it is all about adaptation.so basically even against 3-5-2 flat u have the option to go down flanks by putting red arrows on wide players or u can go through middle with short passes.UR CHOICE