Lay a black thread base down the size 10 3X-long hook, stopping just short of the start of the bend.
Bring the White rubber tubing up through the thread on top of the shank and take one or two wraps to hold it, leaving the thread in front of the bend.
Pull the rubber down to either side and lock it with tight wraps behind the tie-in point, so the tail comes off both sides of the hook without riding up over the top.
Pull the rubber lightly taut — not tight — and snip the tail about one body length long.
Tie in a brown and a grizzly dry-fly hackle together, sized roughly to the hook gap, burying the stems at the front of the body rather than all the way back so dubbing can go behind them.
Wax the thread and dub a slim noodle of black superfine, taking about five wraps behind the hackle first. Use a synthetic rather than rabbit here so this semi-dry does not capture and hold water.
Dub the rest of the body forward to just behind the eye — not thick, but it need not be super thin — taking a second application of dubbing if you need it.
Palmer both hackles forward in close turns, the way the spikes sit close together on a real woolly worm, to the front of the body. Catch them with a couple of wraps, pull back, add securing wraps, snip the forward-pointing fibers, then clip the excess feather stems and tidy the scragglies.
Tie in a second piece of White rubber tubing at the front the same way: a couple of wraps on top, then pull the strands down to either side and lock them with tight wraps, checking the position before locking it in.
Build the head behind the front legs, and if a white spot of rubber still shows through, touch it with a black Sharpie rather than piling on more thread wraps.
Whip finish, then trim the front legs a little shorter than the tail — a bit less than a body length — put a drop of head cement on and spin the fly to spread it, then cure under the UV light.