Hm, I think you start with it's butt and use the left top part of the block to drop down as it's tail, then you can eat the other blocks
I still don't get it, Im not ever good at these types of games
I was stuck at this part for a bit too. I think what they mean is that you start with the butt of the duck and end the level with the six blocks. You're not supposed to eat the six and go back for the butt.