Help against unusual formation "3-4-3"

Hello! I would like some advice against this unusual formation. Playing in CL semi-finals today, in like 11 hours, basically the same quality, I'm 109%, he's 105%. Here's his formation: a weird 3-4-3:
DC - DC - DL

MC - MC - MC - ML

AMR - ST - AML

I have decent players all around, I have one ****ty DC but that's about it. My star players are my AMR,AML. Especially my AML. How do I play against this?
I was thinking 3W-5flat-2 or 3W-5flat-1-1 and just attacking through the left flank.
His star player seems to be his AML. Also looking at his squad, he has the option of playing players in the right flank, at least on defence, but he chooses not to. Could he be showing this formation as a trap and changing it before the match?
If this formation is good could you please suggest arrows and tactics, please?
If not, I'm waiting for other suggestions.
Thanks a lot!