My favorite part was how her hair was in a beautiful and much more complicated knot in the premier episode, then it was a mangled mess after Voyager was thrown to the Delta Quadrant, but they make a show of her fixing it into the simpler knot with her bare hands while walking the corridors from one disaster to another.
Janeway commands, and her hair obeys.
You can kind of see a tuck on the side. My guess is that they still have some sort of structure like a foam piece under the top/front and then it’s pinned in such a way underneath to prevent it from showing, but not in such a way that would prevent the hair on top from free falling. I’m far from an expert though; my only experience is from having my own hair done for weddings and they added foam or mesh pieces in there to fake the shape they wanted.