when you have finished stitching the arcs (pieces of the ring), trim away all the excess fabric to the cutting lines around the patterns. trim carefully.
once they're all trimmed, remove the paper and press the seams open.
pressing them open isn't a rule but i couldn't believe how much easier it was to fit and sew the arcs to the melons when i pressed open instead of to the side. definitely worth the extra few minutes' work.