Start black thread on the long-shank hook and take it back to the bend. Tie in a single red duck or goose slip as the tail with a pinch wrap (it will bunch up, which is fine) then a couple of wraps forward, and trim the front.
Tie in three strands of peacock herl, twist them together loosely (twisting them tight makes them break), and wind a short herl butt; tie off and leave the remaining herl for the front.
Strip the fibres off the end of the yellow chenille to expose the thread core, tie the core in at the front of the butt, then take the thread forward to about four eye-lengths back from the eye. Remember you still need room for the peacock thorax and two bunches of bucktail.
Wind the chenille forward in touching turns to the thread, tie it off and trim.
Wind the same three peacock herls forward to make a short dark thorax section behind the wing; tie off and trim.
Stack a small tuft of natural light brown bucktail and tie it in on top as the underwing, cord the thread up with a clockwise spin first, use a pinch wrap, and keep the second wrap from spinning the hair around the shank. Smooth the area with a couple of wraps.
Hand-stack a slightly smaller tuft of light grey bucktail (just pull out the wild long fibres rather than using a stacker) and lay it on top, a touch longer than the brown. Secure it with medium wraps going back to lay it flat and push the brown down, then tighter wraps forward before trimming.
Optional: set a jungle cock nail on each side at about 30 degrees with a few loose wraps, check the position, and lock them in with tight wraps.
Build a big, hard streamer head with as many thread wraps as it takes, whip finish and cement. A thicker thread keeps the head shorter and fatter.