I like the way you added the squares as an example. I did look at the link you provided (spent some time drooling there). It looks to me like the shadow block is the same size as the pink block. Of course, only cutting the black to make the shadow part, then adding the white blocks of the backing color. I would cut your "pink" for a 5" finished block, then your black at 1 1/2 X 5 1/2 for the vertical strip, and 1 1/2 x 4 1/2 for the horizontal shadow. Cut the two backing squares at 1 1/2 each. (Unless you want to do a set in seam and cut the black as an "L".)
I hope this sounds a bit more clear that mud. I can see what I would do, just trying to give you a visual you can make sense of. :-)