Start black thread about a third of the way back from the eye on a standard-length dry fly hook.
Catch in a pair of grizzly hackle tips for the wings, a little taller than the collar hackle will be, with a pinch wrap. Bring the thread in behind them, lift them up and take several wraps to prop them at 90 degrees.
Split the wings and set them spent: a couple of wraps back to front on the near side, then front to back on the far side. Trim the stray barbs poking forward.
Tie in a fairly long, generous tuft of brown hackle fibers for the tail with a couple of wraps, laying them down slightly, then trim the butts and any curls.
Tie in a small grizzly dry fly hackle for the palmer, well undersized for the hook — roughly what you would use as a collar two sizes down.
Take the thread back to the rear of the body, wax it and spin on a couple of inches of chartreuse Super Fine dubbing, then wrap the body forward to just behind the wings.
Palmer the small grizzly hackle forward over the chartreuse body with the wraps as close together as you like — the more turns, the better it floats. Tie it off and trim.
Tie in the brown collar hackle just behind the wings and take three or four wraps behind the wings, then about six in front, using the feather to help stand the wings back up rather than letting them sweep back.
Tie the collar off, whip finish and drop on some head cement.