Sashings in quilt patterns always used to bother me. Yes, they look lovely:
Yes, they can add a new dimension to your pattern, even creating a secondary pattern:
Yes, they can bring widely varied blocks together into a cohesive quilt:
But they can be a royal pain to deal with sometimes. I don't know why they do this, but almost every quilt pattern I've seen has you sew a large strip of your sashing pieces and setting squares together, to be sewn to your rows of blocks during assembly. But what happens if your blocks aren't QUITE the right dimensions? You end up with a sashing/setting square strip that is longer than your row of blocks, and that can be a pain to work with... especially if you're wrestling with a King size quilt!
I've written a tutorial on how to make working with quilt sashing easy. IMHO, it's just so much easier this way and it's how I do all my sashing these days.
I hope you find this tutorial useful! Happy quilting!