*Gulp* Here it comes. The biggest amount of sewing on this 'able, and in one single serve:
Machine sew the whole thing around the outer edges.
Leave the headdress unsewn, or open, in the following places:
Sew the bottom few centimeters of the flaps twice, to keep the stitching from unravelling.
(Use the reverse button for these areas, if your sewing machine has one.)
If any part of the seam allowance looks too wide, trim it down to about ½ cm - especially on corners or tight areas. It makes it easier to turn right way out. But don’t trim excessively close to the stitching.
Carefully make some little cuts on any curves or angles, without cutting through the stitching. The cuts should be closer together for the sharper angles and further apart for more gentle curves.
Cut the point off any outward-pointing angles, without cutting through the stitching.
Doing these things takes some of the stress off the fabric when it’s turned right side out, and helps prevent pulling or bunching on the curves and angles.