Oh, I have seen some tutorials were after making your blocks you make 2 sashing strips, one for the front and one for the back. On the front you sew the 2 blocks together by machine. And on the back you would sew the sash by machine to one piece the fold your raw edge in and hand stitch it to the other piece of the back. So that both of your blocks are joined together with the sashing between them.
What I am asking is does the back sashing have to be hand sewn?