Andrew West, a linguist, writes about Unicode, writing systems, historic scripts, and tools like BabelPad and BabelMap.
HN links it for Unicode character lookup (the 'What Unicode character is this?' page shows names and code points) and for a follow-up correcting an Ogham mistranslation.
I should first point out that you probably meant Han characters (so called "CJK(V) ideographs", an unfortunate misnomer), and many Asian languages do not use them at all if we are talking about the number of languages.
But yeah, let's talk about strokes first. Almost all Han characters do consist of a small finite number of strokes and the stroke order itself is reasonably canonical... only for a single point of time in one area. There are lots of examples where the stroke order or even the stroke composition itself differ from time to time and among countries. And you won't be able to correctly encode an archaic character which canonical stroke order is not known---you have to guess, and you will be frequently wrong but wouldn't be able to fix that.
So the next possibility is something like character description languages [1], and people tried a lot of them, so much that we even have a standardized description sublanguage in Unicode [2]. And again, there are so many possibilities that we can't have a single canonical description. Andrew West has maintained a comprehensive IDS database for all Unicode Han characters [3], and while sometimes the first level of decomposition looks clear (字 is clearly 宀 + 子) subsequent decompositions are much more ambiguous (is 子 atomic or 了 + 一?). Ultimately this approach takes too much work to be worthy, so most standards including Unicode have treated them as atomic characters with a room for glyphic variations.
[1]…
My first draft was based on the Unicode Power Symbol project. It turns out that was overkill - they just need a Word document with a table of glyph/source/radical/stroke count.
http://unicodepowersymbol.com/we-did-it-how-a-comment-on-hackernews-lead-to-4-%C2%BD-new-unicode-characters/
https://www.unicode.org/L2/L2017/17204-uax45-additions.pdf
They also need a font. I tried to find the original, but in the end just asked Andrew West from BabelStone Han to redraw the characters for me.
It's a hobby project. Finding characters was a side effect of trying to scrape data for Pingtype https://pingtype.github.io (my Chinese learning program). When I tried to scrape characters from the Taiwanese Bible, I found inline JPGs and thought "that can't be right..." which led me down a rabbit hole ending here, exchanging emails with Richard Cook, Ken Lunde and John Jenkins (the world experts).
http://www.lingshyang.com/bible/taiwan_Bible/2ch/2ch14.htm
If you have access to a Chinese-language paper library, please try to help take photos of some characters. Search "please contact" on the BabelStone list for some urgent ones. For example, "U+F2DD Alternative character for Db (Dubnium)" and "U+F2E2 Alternative character for Rf (Rutherfordium)" could be easily found on a periodic table, I guess.
http://www.babelstone.co.uk/Fonts/PUA.html
I remember a time team episode where they found some Ogham script on a stone in an early Christian church now on a fairway on the isle of Mann.
They got photos to the leading professor in Ogham who translated it for them.
I happened to mention this on HN a few months ago in relation to something or other, and a commenter replied to me to explain that that translation was no longer sound, and the current understanding was that the tablet said something completely different instead!
(Found the link they gave! https://www.babelstone.co.uk/Blog/2008/05/throng-of-fifty-warriors-routed-by.html)
It appears to use the good old-fashioned technique of making the edges of each character have the same profile, so any two characters abut seamlessly. You can put your cursor on them to see this.
Also, when I want to know what some string is actually composed of, I like to copy-paste it into https://www.babelstone.co.uk/Unicode/whatisit.html
Edit: Sorry, I answered your question as though you had asked about joiner characters. Still, it appears not to use ligatures, as the characters appear not to change at all if you separate them.
It's "automatic", see https://www.w3.org/International/articles/inline-bidi-markup/uba-basics and https://unicode.org/reports/tr9/
However that algorithm has a couple of flaws in mixed left and right ordered text, and a couple of control characters have been introduced to solve the issue: https://www.w3.org/International/questions/qa-bidi-unicode-controls
Could play a bit in https://www.babelstone.co.uk/Software/BabelPad.html to see how things work.
Tangent:
I recognized the domain and tried to remember why, and now I remember.
I'm working on a game, and babelstone.co.uk has probably the world's most comprehensive (and high quality) set of runic fonts:
https://www.babelstone.co.uk/Fonts/
https://www.babelstone.co.uk/Fonts/Runic.html
https://www.babelstone.co.uk/Fonts/AngloSaxon.html