Mount an Allen N304 in the vice. Tim ties this in a size 18 because the N304 has a shorter shank and a wider gap than average, so the finished fly reads as a 20 or 22 while keeping the holding power of a 16. A real consideration on midges.
Start grey 8/0 thread about one hook-eye's width back from the eye and lay a base. Deliberately leave that front section bare of thread; the foam wing is locked directly onto it later.
Tear six to eight fibres from a large dun neck hackle, line up the tips and tie them in so they extend just past the bend. Clip away the butt ends.
Wrap the thread back down the shank in touching turns. As you reach the tail, lift the fibres with your right hand and place one wrap underneath them to splay them out.
Wrap forward again, stopping short of the bare front section.
Wrap back to the 75% mark and forward again, then back to the 50% mark and forward again. That builds a fine tapered body.
If you want a smoother taper, make one more full pass to the rear and back, keeping every wrap touching the last the whole way.
Cut a narrow strip of white foam from the sheet, then trim the corners off one end so it forms a blunt pencil point rather than a sharp one. This reduces bulk at the tie-in.
Lay the foam over the bare front section and lock it down there, wrap forward, then wrap back over it so that a firm tug will not pull it free, then wrap forward again.
Before tying off, look at the fly from underneath: the wraps should be touching and no white foam should show through on the belly.
Whip finish and trim the thread away.
Trim the foam wing so it reaches back a little less than the body length - Tim keeps very little wing standing off the top of this fly.