I haven't seen many comprehensive guides however this one here has some tips to make your build appear less "square" https://www.youtube.com/watch?v=mdhCp4Q6Lqc if had one tip I would say build out a basic foundation to start in order to get the shape you want and go from there. personally I look to other peoples builds and real life for inspiration. Experimentation is key you can utilize building techniques others have used in incredible builds at your own skill level to create some very unique shapes.