Tail Sparse bucktail or more full marabou with flash of your choice
Body Closed cell foam and least 3mm thick
Hackle Strung saddle
How to tie it
Mount the hook and start the white thread, laying a base along the shank. Put a drop of cement over the thread base to lock it; it stops the thread twisting under the foam later.
Tail: bind a sparse bunch of bucktail at the bend, tips extending two shank lengths behind the hook. Pull out any stray hairs you do not like and rebind.
Add about six strands of flash, roughly tail length, spread around the tail (it does not matter if one side carries more). Fold the long front ends back over the top of the shank and leave them there; they get used at the head.
Cut a strip of closed cell foam at least 3mm thick (White uses 5mm on a size 2, cut 12mm wide tapering to 10mm; a square strip works). Bind the strip on top at the bend, tight and square, leaving two eye-lengths of bare shank at the front for the head tie-down.
Select a medium saddle hackle, not too webby, and bind it in by the tip at the bend with the whole hackle intact. Fold the feather out of the way for the moment.
Cup the foam around the shank and advance the thread forward in open spiral turns, pulling each turn down into the foam so it forms a segmented foam body like a hopper. Do not crush the foam under wraps: crushed foam is lost buoyancy.
Palmer the saddle hackle forward in the thread grooves, passing it under the shank between segments, and take an extra couple of turns at the front so the softer fibres sweep slightly backwards. Fold the stem back and snap it off; a folded stem cannot pull out.
Sweep the hackle back, pull the foam forward over the top, and bind it down two eye-lengths behind the eye with three to five tight turns. Check the foam sits straight across the back, then add a couple of turns underneath to lock it to the hook and a couple more on top.
Bring the long flash butts forward over the top of the foam, spread flat, and bind them into the head groove with three or four wraps. Fold them back, put two or three wraps over the fold, and snip. This is a sighter for the angler, not the fish.
Whip finish over the foam, twice. The first tight knot lifts the foam slightly as it compresses; seat the knot well.
Take the fly out of the vise and snip the foam lip to length (size to taste). Knock the corners off and round the hardened edges: a rounded lip twists less than a square one.
Seal the whip finish with head cement, not UV resin. The foam flexes and compresses, so resin pops off; cement soaks into the thread and shrinks in.