Start black thread in the front third of a size 12 dry fly hook.
Stack a small clump of white calf tail (it never stacks perfectly. Work with what you get) and tie it in as a wing, deliberately longer than the hackle will be. Secure with several progressively tighter wraps.
Lift the wing to about 30 degrees, lay your scissors parallel to the shank, and snip the butts off to leave a taper. Take wraps in front of and under the wing to prop it upright, leaving room for three or four hackle turns ahead of it.
Split the wing with a series of figure eight wraps until the two halves stand apart. With thread this fine it takes several passes. A slight forward lean is fine. The hackle will push them back.
For the tail, grab the tips of a Lady Amherst tippet feather, slide your scissors in and cut about eight fibers off at once. This keeps the tips aligned. Tie them in at the bend, on the shorter side rather than the longer, and let them splay. Trim the butts.
Tie in three strands of peacock herl at the bend, breaking off the brittle first inch or two, and take two turns to build the rear third of the body. Tie off on top of the shank, lay the herl forward out of the way, and move the thread forward.
Wrap the white floss as the mid-body band (up, back and up again for at least two layers so the white really shows) then tie off and trim.
Take the thread just in front of the floss but still behind the wing, bring the peacock back into play, and take two or three more turns for the front section of the body.
Tie in a grizzly dry fly hackle just behind the wing. Take two turns behind the wing and three or four in front of it, using those front wraps to push the wing back upright. Tie off with two wraps.
Wet your fingers, sweep everything back to make room, whip finish, and set the head with a tiny drop of UV resin. Keep it out of the eye. Check with a piece of 4X tippet that the eye is clear.