Check out the blocks around 51 seconds - just before and just after they are in the box.
The set of blocks after the cut is not the same as the set of blocks before the cut.
This is a variation of the old trick you can do yourself with grid paper and scissors. You get one square left over after you rearrange. The key is that the lines don't quite add up and quite a few of the remaining squares aren't full size but close enough to pass for it.
