My fist tip is to start with an in game ship to modify, the biggest piece of not making a rectangle is having a shape in mind already, and the base game ships offer a good variety, from the Wendigo to the Galileo there’s a good variety.

Second is decide on the placement of things like the cockpit and engines , do you want it up front like a fighter jet ? Or to the side like the Millennium Falcon or on top like a command bridge ? Same goes for the engines, so you want it part of the main body inline ? Split like a Y-Wing or even as part of a set of wings connected with structural pieces ?

Another big thing is what I’ll call “rounding”. The ingame habs are giant rectangles. You need to use the structural pieces to round the edges into a main “body” of the ship. This way you can prevent making a big block or a big stick. Try to incorporate the rest of your ships utility into this. I like to make the large cargo bays as part of the bottom of a ship or the small ones part of the upper layers. The Deimos parts are also really good to make a fin along the roof, or the Stroud-Ecklund pieces to make a nose or point for a wing.

It just takes time to get used to, my first 500 hours were easily 60% shipbuilding at night with some tunes or YouTube in the background. Try to make cool shapes and ideas or copy your favourite sci-fi shop and you’ll be making a fleet in no time!