This is what happens when I think too much. I wanted to make an L whose area = the unused area of the containing square. Didn’t happen. If x=the length of the side of the containing square, and y=the length of the size of the 4 squares which make up the L, then … well, it’s too hard to type. The formula is written in the square. What I didn’t count on was that the 4-square L would break out of the containing square. Perhaps a 6-square L would have worked.
Oh, well.