Technically you unlock this achievement by sliding from left to right for 10 seconds without stopping.
Well, for me it unlocked after I tried to climb a corner in one level, using a corner boost (watch some speedruns to see how it works) for a few seconds. As long as that corner is slightly tipped inwards, you should be able to climb on it and the game will think that you're over max speed. Even though you might not be moving at all, or just slowly upwards