4 of your squares need to be the same size.
The 5th square can be:
the same size, which will make a "diamond" shape in the center that extends exactly halfway up each inner seam of the finished 4-patch block;
a bit smaller, which will make a smaller "diamond" shape in the center of the finished 4-patch block;
or a bit larger, which will make a larger "diamond" shape in the center of the finished 4-patch block.
Try all three and see which you like.