Lay a base of black thread back to the start of the bend.
Catch a single slip of red duck on top of the shank at the bend as a long tail, setting it upright as you would a wing rather than letting it lie flat. Lock it with a couple of wraps and bind the butt forward, keeping thread wraps to a minimum so there is no lump under the flat tinsel body.
Snip a few fibres from the end of a length of small black chenille and tie it in at the bend. Take two wraps side by side for the butt, stacking one on the other if you want it fatter, and snip the excess. In trout sizes you need the small chenille; medium only works on size 6 and up.
Catch the silver Mylar tinsel in at the front, silver side toward the hook and on the near side, then take big open wraps back to the butt and open wraps forward again to keep the underbody smooth.
Wrap the silver Mylar tinsel forward in touching turns with no overlaps and no gaps showing. Catch it off at the front with a couple of tight wraps, snip, and take two more wraps to lock it.
Take about 15 brown hackle fibres from a soft feather for the throat, reaching to about the hook point or a touch shy. Pinch-wrap them under the shank, take one more wrap, check they are coming off the bottom, then one more to lock and snip the excess. If the throat lies close to the body, tug it down a little without pulling it out.
Leave the thread at the back of where the head will be. Gauge the width of the wing slips by sliding a slip past the hook held in a pair of spring hackle pliers; it may come out a touch thick, so take a couple of fibres off. Line the tips of the two red duck slips up.
Measure the wing to about the hook bend. Pinch the slips and the hook together in your material hand, take one pinch wrap without pulling tight, come back up the near side and pull up while moving your fingers forward, then a second wrap. Check the position, then take a couple of tighter wraps going forward.
Cut the wing butts as close as you can and singe the stubs. Take the thread back to the eye and ramp it up to build the head, then whip finish with three or four turns, snip, tidy any stray fibres, and add head cement.