I worked it out - the rectangles are all the same size - to make a square, the length of the rectangles need to be the finished length of the square plus 1/2", the width needs to be 1/2 the finished width plus 1/2", so a 4" finished square needs to be 2.5x4.5", a 5" finished square needs to be 3"x5.5", a 6" square needs to be 3.5"x6.5", an 8" square needs to be 4.5"x8.5", 9" needs to be 5"x9.5", 10" needs to be 5.5"x10.5", a 12" square needs to be 6.5"x12.5"- Just make sure you fold the middle square in half and catch it in the seam like she shows in the video - really easy peasy, don't need to overthink it.