For this achievement you need to hit 6 fours consecutively in an over (if a no-ball is bowled there is no need to hit 7 fours, however they must be consecutive).
Play a Test match on easy and load the opposition with batsmen (get rid of any good bowlers).
For short balls get on the back foot, otherwise front foot and press B to go for the slog every time. Aim for the longer boundaries (passed the bowler) but make sure you're away from any fielders. By aiming for the longer boundaries you're less likely to hit a 6.
You can save the game after each ball and load up if you don't hit a 4. I didn't need to do this but you may want to save after hitting 4 or 5 fours in a row ... just in case.