It is easier if the board maintains a steady course during the duck. If you head way upwind where there are waves then it might be hard to do that, so pick a flat spot or plan to have it over by the time you ride up the downwind side of a wave.
Consistent wind is more important than totally flat water. Any shifts in apparent wind direction (which can be induced by shifts in true wind speed) that occur during the move will make it much harder.
The big trick is luffing the sail with the back hand, pushing when you might think you should pull. That is, if you have let go of your front hand and the mast is headed for the nose, then you need to push on the back hand to bring the sail back. If the wind is about to catch the back of the sail you need to pull. This is fine-tuned motion, although the closer the back hand is to the clew in the beginning the bigger these motions need to be.
So switch your feet, out of the straps, getting your body far forward without getting the sail far forward. Stay on your toes to keep the board tracking straight. Guide the mast down as above, a lot of it's windy, less if it's less windy. Use the old front hand to throw the clew back. Yes, also down, but mostly back so that mast comes back up far enough towards the tail that you won't get slammed.
Finish it like a regular tack and then smile at those in the know. Though some would differ, I think this one is harder than a Spock.