Thank you all for your help!!

LindaM and others who piece this way... thank you! I've struggled with the few backs I've made. This makes a lot of sense!!

Aaaaany way you want. I don't add another piece down the middle because if the back shifts at all while basting or quilting, it will be off-center and look like an oops. So I make my piecing off-kilter and it looks deliberate...which it is! Here are 3 examples

Here's some more backsides for ideas .......

I'm going to try John Flynn's diagonal method - but i'll probably put another fabric between the 2 pieces. I almost never use just one fabric on the back of the quilt. I usually put something from the front of the quilt on the back. His method would work very nicely for wall hangings, though, where you don't really care a lot about how the back looks. You could jazz up the back with a band of color from the front, and make a BIG DEAL out of the diagonal cut instead of trying to hide it.

Thanks for the link Linda. I have never heard of diagonal piecing of a backing. I will have to try it!

I am so lousy at math and trying to visualize ---- so I just buy wide quilt backing and never worry about it. It is actually not more expensive to buy than regular width fabric.

Oh I love these pieced backs... so much more interesting than a plain back!! Baloonatic (love that, btw :D ), I don't see how you stitch the sides to the diagonal piece, but I'm thinking about it...
It looks great... all those backs look great!!

Wait a minute... do you use the Flynn diagonal method?? Reading back through these comments made me realize... I'll check it out!

Beginner question...............
Wouldn't it be difficult to cut and sew flannel on the diagonal?
I love flannel but have a hard time with it.

I would cut the flannel in half and sew to each side of the remaining whole piece. Looks better, but you can just cut off what is needed for the width and just sew one piece to one side of your quilt but I think it looks better with a piece sewed to each side.
IdahoSandy