Forwards
The attacking line-up for Arsenal should ideally be: Left winger: Pierre-Emerick Aubameyang, Right winger: Henrikh Mkhitaryan and Centre-forward: Alexandre Lacazette.
Arsenal's weakest positions are wingers. So, Emery must improvise something. Henrikh Mkhitaryan is a very versatile player who can play as an attacking midfielder and can also play on the wing. So, in this formation, Mkhitaryan should play on the right wing. This position isn't strange for him.
Aubameyang prefers to play as a centre-forward. But, in absence of a really good winger, he should start on the left wing position. It's important to say that he played in this position at the beginning of his career. He is very quick and we can expect him to cut inside because he is right footed.
And finally, Lacazette should be Arsenal's main attacking force in this season. His first season at the Emirates was good but not brilliant. He scored 14 goals and provided 5 assists in 32 matches in the Premier League. He lost his spot in the starting lineup in January when Aubameyang came in the club.