Piecing curves is a quilt technique designed for those tricky curved pieces. By using this quilt technique, you'll save yourself some time and frustration.
When piecing together curved quilt patterns, fold each curved piece in half to find the center of the seam. Clip the concave curve 3/16 inch deep approximately every 1/2 inch along the curve (clip more often for a very tight curve, less often for a gradual curve). With the two pieces' right sides together, match the center of each seam and the end points. Pin carefully. With the concave curve on top, stitch the pieces slowly, easing the fabric so that the edges stay even.