Chapter 3 - Chamber 10
Learn the level by doing it a few times at a regular pace, then try and follow the video as best as you can, and you should have no problem getting this achievements in a few tries. Can easily be done with 5 seconds to spare.
The timer begins when you exit the elevator, and stops once the cube touches the pad, unlocking the achievement if done quickly enough.
Note: With the new update, you can get this achievement in Challenge Mode on "The Return: Ricochet"