I like to use starch when cutting AND sewing bias or other less-than-straight edges, such as half square triangles. Also when the two cut edges you want to seam together are slightly different lengths, I pin the two pieces together at each end making sure they are even..put the slightly longer side next to the feed dogs and it comes out even. Sometimes I just tug a little bit on the shorter piece if it is only a little bit off. I find that pressing seams will make them come out looking good, as well.