only during the Bewitched event?
I used most of my dry pieces of wood when the event was not active during all the year and I got the achievement today (1 day after the event finished with reward active).
It would be nice someone can confirm this achievement can be gotten during any time of the year to edit the spoiler if needed.
As it's possible to add wood to the slide whenever you want to, it's also possible to gain the achievement whenever you want to (as long as you have Dry Pieces of Wood to your disposal of course). Edited it for you. -- Wouterboy (talk) 13:10, January 17, 2014 (UTC)