I found that i had to do it in the square when the picture (or shape) appears and do it quickly – save before you build and that way if you dont make it, then turn off the DS and then back on and try again – practice makes perfect.
Btw, i am up to where you take skye to the temple and i have just gone up the inital stairs into the room before the two switches and i cant get her down to go through the door!!! How can i get her down off the ledge?? Help anyone!