Start thread mid-shank and run a thin base to the bend.
Tie in a single strand of root-beer diamond braid or Krystal Flash at the bend and leave a short glassy tag sticking off the back as the trailing shuck, no longer than half a shank.
Build a slim, slightly tapered body of tying thread forward to the 70% mark.
Tie in a clump of natural dun CDC fibers as an upright wing at 70%, standing them up with a few wraps in front; keep it sparse but let the fibers fluff for visibility.
Tie in a dun hackle behind the wing and take just 2-3 turns, then tie it off, so the fly rides low in the film.
Whip finish at the eye and add a tiny drop of cement, keeping it off the CDC.