Wales captain Elliot Care, Ant Walker, Ashton Robinson and Connor Davies also performed brilliantly in the first half.
Moxon saw Mike Butt and Hugh Worthington lose.
Serbia fought until the end, but failed in attempts to get on the scoreboard and the final play of the game saw Joe Coupe-Franklin cross for the first try.
Wales are now 3-0 against Serbia and Wales’ total points are 186-8.
Before Wales win in his absence, boss cares Criticized the qualification process for the 2026 World Cup.
In a statement, Wales RL said Batley Bulldogs head coach Moxon would remain in charge of the team for Saturday’s clash.
“Everyone at Wales Rugby League wishes John all the best and asks everyone to respect his and his family’s privacy so he can focus on his full recovery,” Wales RL said.