So, how do you get it in two minutes? It's very simple...
First, you want a group of at least four people, a maximum of six, including yourself, and all of you need to be in a party and be able to communicate with each other.
You need to designate one player as 'The countdown guy'.
All players need to go to 'Find Game' in multiplayer, and highlight the Halo: CE playlist, but do not select it yet.
The countdown guy needs to do a small countdown of "3, 2, 1, NOW." When the countdown guy says "NOW", everyone needs to press

to search the Halo: CE playlist. It is
EXTREMELY important that
EVERY player searches at
EXACTLY the same second, as this will increase the chances of you being matched up considerably.
Luckily, Halo: CE has a maximum of 6 players, and a minimum of 4, which is perfect for what we're trying to do.
In the party, when you're searching, you want to call out the searching lobby's status changes, e.g. 'Players Found', 'Joining Game', etc. If you're getting the same status as your friends/boosting partners at exactly the same time, it's highly likely you're in the same game.
When you're mostly together in the Halo: CE matchmaking, choose any CTF game.
You now want to split into pairs, with a red player and a blue player being in each pair.
Each pair goes to a different flag.
You will now need to designate players;
The person who is the SAME COLOUR as the flag, is the 'flag retriever'.
The person who is the OPPOSITE COLOUR as the flag, is the 'flag grabber'.
The 'flag retriever' needs to stand EXACTLY on the flag spawn/'home' point for the flag.
The 'flag grabber' needs to stand next to the 'flag retriever'.
You will notice the 'flag grabber' picks up the flag when standing here. Now, face the 'flag retriever', and rapidly press

* whilst facing the 'flag retriever'.
*If you do not have RT as your 'flag throw' button on your control scheme, substitute RT with whatever button you have as your 'flag throw' button.The 'flag grabber' needs to press his 'flag throw' button as fast as he can and they'll find that they will get multiple 'Flag Taken' medals very quickly. The 'flag retriever' will be getting multiple 'Flag Returned' medals very quickly. Keep doing this until the achievement pops in game.
It's THAT easy.