Start the red thread and lay a base back to almost the hook point, not all the way to the bend.
Catch in two strands of pearl Krystal Flash at least a shank length long: catch them on the near side, fold them back over with a couple of wraps on the far side, and snip the tag. This is the first part of the tail.
Take six white hackle feathers and catch them in on top at the tail tie-in. The tips do not need to line up. Leave the butts running at least half the shank so they cannot pull out, trim them, and smooth a slight taper with thread.
Tie in the first red hackle concave side toward the hook, held roughly perpendicular, with a little red thread still showing behind it. Advance the thread to where the red will end and take about four turns, one right in front of the other. Catch it in with two wraps, hold tension, pull the fibres back and add a couple of extra wraps, then snip everything forward of the wraps.
Tie in a white hackle the same way, concave side to the hook with a little bare stem, so the first wrap sits right in front of the red. Take four or five turns, catch off with two wraps, pull back, add extra wraps and snip. A little red showing through is fine.
Smooth the area and tie in the last red hackle, matching the first in fibre length and density, leaving room for a head. Take four or five turns, catch off, pull the fibres back and snip.