Start yellow thread behind the eye and take it back to about above the hook point.
Tie in eight to ten light ginger hackle fibres as a tail and snip any curly butts.
Bring the thread back to the front of the tail, wax it, and spin on superfine sulphur yellow dubbing. Wrap a slim body forward to about the 80% point.
Cut a strip of 2 mm yellow foam about a hook gap wide, flatten it, and tie it in on top just behind the eye with a couple of wraps. Close to the eye but not on it, or you will not get tippet through.
Fold the foam back over on itself to form a low loop, the 'hat'. And lock it down with a couple more wraps, then one wrap slightly further forward to set the angle. Size the loop to taste: enough foam to float the fly, not so much that it looks like a beach ball.
Trim the foam excess close and bury the last nub under thread.
Tie in a light ginger dry fly hackle immediately behind the foam. If in doubt about size, err one size smaller than usual. The foam, not the hackle, is what keeps this fly up.
Take four or five turns of hackle and tie it off behind the foam loop.
Whip finish behind the foam with four wraps, then snip the hackle stem.