Every "hole" in the design is done by piercing a small hole with tiny drill bits (generally, I use ones that are 0.7mm), then passing one end of the blade through the hole before attaching it to the saw. The blade is then "trapped" in the hole and you can cut out the shape from the "inside" (I'm not sure how much sense my description makes, I'm not very good at explaining things)

So the lines in the wings and the hole of the tail are all made with this same process. This is actually the part that takes the longest, cutting the various shapes is relatively fast, but each hole inside the design requires detaching the blade, passing it through, reattaching it to the saw, and adjusting the tension (which is very important, and funnily enough is done in good part by listening to the pitch of the noise the blade makes when flicked). One of the most tedious crafts I've made was this one, simply because of the amount of holes (the pattern is not mine, I just printed it and used it like that):

I don't know how long exactly, it's been years since I started but it's just been a hobby so I have been pretty irregular in how much I do it. It's definitely less complicated than it looks (the technique I'm using of cutting a metal plate, not jewelry making in general), the biggest requirement is a bit of accuracy and focus, and the tools (which I was lucky to have access to, when I wanted to start).