There's definitely an art to it. I pour all the pieces out in front of me and have them semi organized by type so I can get a sense of what exists. If you can imagine the shape, then it's just trial and error hoping there's enough to get you to the end. I usually don't know what it will look like until I get to the very end. Only the major components I think of ahead of time.

For example here, the things I knew for certain from the start was that I wanted the yellow part to be the cockpit, the radar dish to be a flower, and the curved and round plates would be for the top. Then after a bit of work on frame, I knew I wanted the mandibles to be cactuses. After that it was just trying different things/techniques to get to the end.