Our home form continued to shine, as we knocked four past West Ham in the second half, in this Premier League tie.In the Sunday sunshine, Arsene opted to give his Europa League lineup a stretch of their legs, and it included some surprises.Chief among them was the choice to leave Pierre-Emerick Aubameyang on the bench. The Gabon striker is cup-tied for the Europa League so starting in the Premier League has been his only gametime, but Wenger wanted to play the eleven that would most likely take to the field versus Atletico on Thursday, with Welbeck and Lacazette given the attacking roles.Mesut Ozil was another who was left out, another bout of illness struck the German to see him out of the matchday squad. Aaron Ramsey was given the playmaker role, with Granit Xhaka and Mohamed Elneny in the centre of the park.Petr Cech and Jack Wilshere were also absent through injury, but it didn’t stop us from being the team in the ascendancy from the offing, as Laurent Koscielny nodded just wide from a Xhaka corner in the best chance of the opening ten minutes.In fact, it was the best chance of the half - for either team. Midfielders were cancelling each other out, moves were falling into opposition hands and defences - although it was close at times - were coming out on top.The only other noteworthy incident of the half was a nasty looking injury to Mohamed Elneny. He duelled for an airborn ball with Mark Noble and came off worst as Noble’s leg followed through. It caused the Egyptian to leave the field on a stretcher, and he must be a doubt for Atletico on Thursday.The half time whistle came and the match result was on a knife edge.Six minutes into the second half, and we had broken the deadlock.It came from a set-piece - which meant we are currently the most prolific team in the league from set-plays - Granit Xhaka fired in a corner and Nacho Monreal - probably our most consistent player this season - caressed in a first time volley.It was a cracking finish, but less than ten minutes later, West Ham were level again.A ball in from the left saw Ospina dive to punch clear ahead of Marko Arnautovic. West Ham regained possession, and Arnautovic found space receive a pass and drill hard and low into the far corner.The good news was that the game had become a lot more open, there was space to be had in the centre, and that would surely benefit us rather than our opponents.Pierre-Emerick Aubameyang was introduced soon after the Hammers goal, replacing Alex Iwobi. It would mean Aubameyang would rekindle his partnership with Lacazette up top - we just needed to supply them.It appeared as if Aubameyang would take up the left spot of our attack, leaving Lacazette up top. The problem was that time was ticking, and the score still hadn’t changed. We needed to win this game, as Burnley were simultaneously drawing with Stoke and the gap wouldn’t change - they could still catch us.Danny Welbeck tried his luck with a curling effort that Joe Hart was at full stretch for, but the net wasn’t rippling yet. A little over ten minutes to go and the score was all square.We then grabbed the lead!Lacazette broke forward and put in a ball that just evaded Aubameyang, but the ball broke out wide to Aaron Ramsey. The Welshman curled in a cross and Declan Rice left it for Hart. The problem was that Hart had told Rice to clear it. It curled in and we had the initiative. Minutes later, it was three.Welbeck found space and after what seemed like a million passes, we looked like we had worked it across the box a little too much. Lacazette didn’t agree though, and he lashed an effort that nicked off Aaron Cresswell and past Hart - the fifth consecutive home Premier League game we had bagged three goals.That prompted the arrival of Andy Carroll, but the big West Ham striker had less than five minutes to do something. We were coasting now, and with Burnley dropping points against Stoke, it would give us some breathing space, especially with our next PL fixture being at Old Trafford.We weren’t finished though, Aubameyang played in Ramsey, who went to the byline in the box and cut back to find Lacazette. The Frenchman’s first touch took his marker out of the game and allowed him space to fire home emphatically. The full time whistle blew and we had got the win that signalled the first game of Arsene Wenger’s goodbye. It was also the first domino we needed to fall in order to finish this season the way it needs to be finished.