Giroud had gone seven games without a goal before Sunday but his glanced header in the 65th minute took his tally to 11 for the season.
Flamini hailed Giroud's work ethic and believes he brings more to the team than just goals.
It's also important to be strong defensively because that makes the difference at the end of the yearMathieu Flamini
"Olivier [Giroud] has played a lot recently and it's never easy," said Flamini. "He's giving a lot to the team because he is a very hard worker so I was very happy for him because he really deserves this goal.
"When you're a striker you always want to score but he always comes back and gives a lot defensively."
The victory meant Arsenal will end 2013 at the summit of the Premier League but the French midfielder insists the Gunners still have a long way to go and must stay strong defensively if they are to remain in contention.
"It's only half-time," he said. "But at the beginning of the season, especially after the Aston Vila game, if we were told at half-time we would be top we would have signed [for it] straight away.
"We have a very offensive team but it's also important to be strong defensively because that makes the difference at the end of the year."Copyright 2016 The Arsenal Football Club plc. Permission to use quotations from this article is granted subject to appropriate credit being given to www.arsenal.com as the source