Cut the center strip horizontally 2 1/2” in from the top and bottom.
Switch the center squares.
Sew the center strips back onto the new center square, right sides together and press out.
Sew the side strips onto the center strip right sides together and press out. Don’t worry about lining up the side strips as you’ll be trimming off those extra pieces anyways.
Trim off the top and bottom first, and the sides 1/4” or so until you have a square block that is 7 1/2” square.