This Achievement sounds pretty hard initially but it is in fact, extremely easy.
First, you can possibly do this the "proper way" by racking up stunts off ramps but here is the "EASY" way.
Simply start a Stunt Showcase event on any track. When you start racing all you need to do is press and hold
to perform a high jump. While in the air press
or
as these are the two quickest stunts.
Now as you drive along keep doing that for the entirety of the race. Save your boosts for hitting the ramps. Remember, press and hold
at the end of the ramp to get height. From these you should be able to get 3 or 4 stunts using
and/or
.
The Achievement tracker won't keep your progress so the only way you'll know you have done enough is at the end of the race when the Achievement pops, or doesn't if you didn't meet the requirements.