In Rosa's method, she uses a fusible interfacing on the wrong side of the fabric with the shape she wants. The 1/8 to 1/4 turn under has fabric glue put on and the little tools are used to push /turn the seam allowance over onto the interfacing to stick. She gets really nice shapes and I would think the iron on interfacing and gluing the seam allowance would really prevent any edges from fraying on inside tight curves.