You can play short unranked tournaments to get this achievement. You just need one other player.
The quickest way to get through it is to create a player match using the following settings and choose one player to pick up all the flags in any given round (you can alternate who picks up flags each round to prevent boredom):
TYPE: Pickup Tournament
MODE: Arena
LENGTH: Short
RULES: Flag
Each tournament is three rounds so to play ten tournaments you'll have to play thirty rounds in total. It should take about an hour.