Yikes, hate that!
I starch the bejabbers out of anything that's going to have bias edges on the outside. Then ease in the bias by putting it next to the feed dogs and stretching the sashing or border
very slightly as I stitch it on, to help take up the ripples. If I'm stitching one bias edge to another, I match the points that need matching and stretch both of them very slightly as I sew.
When it's all done, I steam the darn things into submission.
