Stop and turn your fabric, often too. Leave the needle down, lift the presser foot and turn. Trying to just quickly turn your fabric under the presser foot can cause puckers. It is a pain to start and stop, but you will be happier with the results.
Don't forget to mirror image the stitch if necessary :wink: the straight stitch goes along side the applique and the zigs go on it :D:D:D