You could argue JWST will be doing self assembly on orbit with the deployment of the primary mirror. There is some very fine wave front adjustment that needs to happen there. They are putting a 6.5 meter mirror on orbit! That alone puts it in a tie for the 14th largest telescope primary mirror when you include Earth-based ones. Very impressive in my book.

https://en.wikipedia.org/wiki/Optical_Telescope_Element

https://en.wikipedia.org/wiki/List_of_largest_optical_reflec...