Slide the 3.5mm gold slotted tungsten bead onto a size 12 barbed nymph hook. Catch the thread in the slot of the bead and wind around to trap it, which holds the bead in place.
Using the tag end held at 45 degrees to keep the wraps tight and smooth, lay a thread base right back to near the bend.
Chop off two brown goose biots for the tail. Each has a slight curve, so set them with the curves facing away from each other, pinch them level, and bring one to each side of the hook.
Take a loose wrap, then wind on gradually and tighten so a biot ends up on each side of the shank. This is fiddly and takes practice; pull the thread base tight and then manipulate the biots into position.
Tie in the copper wire along the side of the hook and wrap back to the base of the tail. The classic uses silver tinsel here, but copper wire works and is more durable.
Tie in two strands of peacock herl alongside the wire, right back at the tail.
Wind the herl forward in tight touching wraps, coming right underneath the hook on the first turn, up to just short of the bead, then tie off and pinch the ends away.
Counter-wrap the copper wire forward over the herl so the rib protects it rather than bedding into it, tie it off, and helicopter the wire to break it cleanly.
Take a brown or tan CDC feather, pull the fibres back to expose the tip, and tie it in by the tip angled 45 degrees back. The tip is so soft you can just bind it back rather than snipping it.
Grip the tip with hackle pliers and wrap two or three turns forward, pulling the fibres back before each turn so they sweep rearwards. Work the thread between the fibres and tie off with as few wraps as possible, then pull the fibres back and snap off any excess.
Tie in the two white goose biots one at a time for the wing case, each angled 45 degrees away from the fly and about two-thirds of the shank length, using only a couple of wraps each.
Pull them back, snip the butts off as close as possible, and check they are still sitting correctly.
This is the one fly where minimum thread wraps matter, so put a drop of superglue on the thread near the bead and whip finish over it. Biots are slippery and would otherwise take a million wraps to hold.