there is that horizontal black foam blade which isn't on the gurgler. Looks like that is put in before the upper gurgler foam is folded down and perhaps glued to it. Is the black foam put on the shank by sticking a hole in the centre with a bodkin then pushed over the eye through that hole?
Yes, the horizontal foam is key. I poke a hole in the middle, slide it on the hook, double it over the eye, and secure it down by wrapping thread over 1/4" of the foam onto the hook shank, and then glue as well. Once that's done, I throw in all my other other materials and tie down the foam for the back.
Make sure that the foam for the back (pink stuff) is super wide, wide enough to fold over the edges of the black horizontal foam. The thing I have found best for securing the top piece of foam is actually shoe goo. Normal glue didn't work well and allowed the foam to lift and break (it also didn't hold its shape which affected the action) after a day of casting and catching fish. A little shoe goo under the lip when you put it down, and some on the sides will hold the top down well and keep it there, in shape, forever.