An easy way to get this is to start a single player race and drive with the 1972 Ford Escort. Any car could work but the Escort is really unstable and thus easier to tip over. Track doesn't matter but with A.I.
Start the race and bump sideways against your opponents , preferably in a corner. This will make you tip over and when you land on your side or roof your wheels won't touch the ground and you will get the achievement within a second.
This worked for me even without trying so I hope that this will work for you too
Thanks to AngelTiddles
for confirming that you can land on your roof to get this achievement !