Not much of a solution as it's pretty self explanatory and you can change the bot settings in the main menu.
Set the bots to fill and pick the desert map. Bot difficulty to 0% (Derp) and rounds to 4. Also set the time limit to 15 to make things go a little faster. Finish both rounds without dying and the achievement will pop. Sit back and shoot them and your team should do most of the work. Don't move up into the combat as you may die instantly.
Must be more than 2 rounds for the achievement to pop. Don't ask me why, because I have no clue. Took me a few attempts to figure this out.