You can add the half white hexagons to the edge for a straight edge. You can also create a "facing" edge or do the "pillowcase" edge. The facing is just like a facing for a collar where you sew rights sides together around any irregular object and then clip the curves/corners and turn right side out. This method allows you to do all the quilting first and then the facing/strips are turned over to the back and hand stitched to the quilt back.The pillowcase is when you lay the odd edge top, right side down on top of the backing (right side up) with the batting under the backing. You stitch around the edge following the odd shapes and leave a section open to turn right side out and then quilt it. You should be able to find a site for both doing a "facing" edge or "pillowcase" style edge.