Small dolls such as Barbie are hard to sew for. I have discovered a new way to make a collar. Iron on lightweight fusible interfacing to the wrong side of your fabric. Trace the collar onto the interfacing side of the fabric. (Do not cut out!) With your sewing machine follow your trace lines by stitching a top stitch. I always like to add a touch of fray blocker around the outside of the stitching before cutting out. Let the fray blocker dry completely. With small sharp scissors, cut out your collar close to the edges of your stitching. Now you have a collar without lumpy seams.