The first bias-edge-blocks quilt I made had all of the classic problems, wavy edges, wider on top and bottom with a more narrow center, etc. I learned that starch is my friend! Starch (or use sizing) before cutting your fabric, then handle each piece as if it were a butterfly. I also straight stitch around the entire edge of the quilt before pin basting and quilting. Once you get the hang of it, you will love this technique.