For machine work, the lack of repeatability is a killer. Maybe for hobby use on a home wood router sort of setup, where you are going to manually indicate in each job anyway? In a production situation, repeatable workholding is not optional or you're going to burn loads of time on setup.

> It’s usually a pain to hold irregular parts without a flat surface. In fact, I can’t think of a good way to do it at all.

Jigs/fixtures, side clamps, strap clamps, toe clamps, Mitee-Bite-style off axis cams, plenty of options. There are commercial manufacturers of flexible workholding solutions similar in spirit to the OP but those are generally targeted at QC purposes where you'll be running a CMM of some sort over the part and so no reference surface on the fixture is needed: https://engtechgroup.com/technical-partner/hyfore-workholdin...

Yeah, I’m definitely speaking to hobby grade workholding but at about $1.5k that’s where this would be used anyways. Also why wouldn’t it be repeatable? If you have a stop set up on one “face” of the fractal vise, wouldn’t it always hold the item in the same configuration (at least theoretically)?

I’m not sure what mitee bite is but the other suggestions are not realistic. Side clamps wouldn't be able to hold something shaped like a 2D Christmas tree rigidly. Strap clamps are not nearly rigid enough even for hobby grade work. Toe clamps won’t work for anything rounded etc. All of the above can be held with the fractal vise.

Well, as a final argument I would ask you look into any hobby or commercial or industrial machine shop on any scale and note the complete absence of these vices, despite the original patent being issued 100 years ago.

I use strap clamps on a hobby mill to hold steel while being machined, they are plenty rigid.

Hey man! Legendary machine shop Youtuber This Old Tony just release a new video that made me think of you :D

https://www.youtube.com/watch?v=9FVavOy4GUw

Here he's attempting a side clamp design but demonstrates several other solutions commonly used for the home machine shop. Hope you find it helpful!