Sead Kolasinac was a surprise addition to Arsenal's starting eleven who had been strongly linked with a move to Turkey in the past week.
There were also chances for game time for Nuno Tavares, Mohamed Elneny and Aaron Ramsdale, who was impressive in his debut between the posts.
A hat-trick from skipper Pierre-Emerick Aubameyang showed glimpses of his former self as well as Nicolas Pepe, Bukayo Saka and Alex Lacazette adding to the total.
A more confident Arsenal:
The Gunners' had 14 shots, nine of which were on target and six in the back of the net. New signing Martin Ødegaard provided more service to Bukayo Saka and Pepe, who were both on the scoresheet.
Both Aubameyang and Lacazette, later on, scored in their first full start since recovering from COVID 19.
The bonus of a packed away end at The Hawthorns urged the players on to shoot more and were seen celebrating with the fans during their goals in the second half and at the full-time whistle.
West Brom made 11 changes to the side that beat Blackburn Rovers in the Sky Bet Championship last weekend.
Robert Snodgrass was handed his chance whilst many academy players featured including prospect Ethan Ingram.
The young side with an average age of around 22 years still managed to produce 11 shots, but the majority were saved by Arsenal's new £28million keeper, Ramsdale, who after a small blunder in the first half, found his rhythm rather quickly.
The Baggies face Peterborough next on Saturday in their race for promotion back to the Premier League and Ismael admitted that it was not their strongest side in the pre-match interview and that it was a chance for some young players to try to break through into the first team.
A happy return for Auba:
Prolific striker and club captain Aubameyang made his first full return since testing positive for COVID 19 before the Brentford match.
It took him just 17 minutes to get his first goal, with all the work coming from Saka, who's attempt rebounded into the feet of the Gabonese man to tap in.
The second goal came right on the brink of half time when Pepe darted through on the right and was unlucky to see his attempt strike the right post before rebounding yet again for Aubameyang to pounce on.
The 32-year-old made it a hat trick when former West Brom loanee Ainsley Maitland Niles played it out to Pierre on the left who cut in and finished from the edge of the box with a trademark finish, a wonderful finesse into the top corner beating Alex Palmer easily as he wheeled off to celebrate with the travelling away fans.
The Gunners' have a very difficult challenge coming next however as they look to get their first points in the Premier League but in doing so will have to dethrone reigning champions Manchester City in the early kickoff on Saturday.