I can sew tolerably well and at one point in my life I toyed with the idea of selling squid shaped backpacks (presumably on Etsy). (The tentacles would wrap around the wearer and serve as straps.) I started by drawing a few sketches and then I needed to figure out some way to make a pattern that would produce the tricky compound curves of the body.
I sculpted a scale model of the body in clay, then covered it with plastic wrap and applied a very thin layer of clay on top of this, simulating cloth. Using a knife, I carefully sliced the thin clay into gores, doing my best to select contour lines that would result in good geometry. Laying the thin pieces out flat on a flatbed scanner, I was able to produce a good scale image. I next used Adobe Illustrator to trace the clay shapes and printed them out on paper. By cutting the pieces out and taping them together, I was able to see if they produced anything like the shape I was trying for.
The paper pattern was pretty close, but needed some adjustments, so I tweaked the illustrator files, reprinted, and reassembled the paper pieces until I had geometry I was happy with. Next I printed the pattern out full size and made a first prototype out of nylon cloth. My initial pattern featured curvy tentacles which proved fiendishly difficult to sew and invert, so I straightened them for my final iteration.
At this point I decided to shift priorities and work on other projects instead as it was becoming clear that the final product would be fairly labor intensive and not something I would want to mass produce. I might still return to this project though, and have kept my patterns and prototypes.