Start Sumo 30 den on the curved emerger hook, run it back to the bend, and tie in the Crystal Body Thread for the rib.
Tie in Mojo Yarn and wind it forward to the 60% mark. The tyer notes this can be dubbing, thread or anything you have. The body is not what makes this fly work.
Rib with four or five open turns of Crystal Body Thread and tie off. It segments the body and adds a small live sparkle without any bulk.
Now the part that matters: stack a bunch of grey CDC and a bunch of yellow CDC together and tie them in at the 70% mark as an upright shuttlecock wing, tips up.
Two colours is the entire point. Yellow shows against dark water and shade, grey shows against glare and bright sky, so whichever way the light goes one half of the wing stays visible and you never lose the fly.
Take a few thread turns in front of the wing to stand it up, whip finish, and trim the butts short. Fish it in the film, dead drift, to fish taking emergers.