Start olive thread behind the eye and run it back to the start of the bend.
Strip about ten barbs from a medium dun hackle feather and tie them in at the bend as a tail, at least one body length long, keeping them on top of the shank. The butts are short enough to simply bury under thread.
Move the thread to the 75% point and tie in a single strand of light dun Z-lon for the wing, longer than you need. Go straight into several tight wraps, take them back a short way to lock it, then trim off the rear half of the strand. One three-inch piece of Z-lon will make several flies.
Take a few wraps in front of the wing to stand it up at about 90 degrees. You can fine-tune the angle later with the hackle wraps.
Take the thread back to the tail, wax it, and spin a thin noodle of olive dry fly dubbing. Thinner than you think, this is a size 18. Wrap a slim body forward to just behind the wing.
Tie in a medium dun dry fly hackle behind the wing, barbs one to one and a half times the hook gap.
Trim the Z-lon wing to length before you wrap the hackle, just slightly taller than the hackle will be.
Wrap two full turns of hackle behind the wing and two or three in front, tie off and hold everything back to make room. It does not take much hackle to float a fly this small.
Whip finish quickly before any barbs spring forward, snip the hackle stem, and clean up any fibres crowding the eye. Check you can still get 6X tippet through.