I have compiled eight short stories and one poem into a book that I’ve published online (at Amazon, as well as other online bookstores). The stories are all the ones I published over the last few years. The poem is new (well, old, but I’ve never tried to publish it anywhere).
I was interested to find out how self publishing works. I’d say it’s not too difficult to get from the finished manuscript to a pretty good-looking book, and then to get it onto an impressive list of sellers.
Formatting is probably the most difficult thing. For reading on Kindles or the like the book needs to be in a dynamic format so font sizes can be increased/decreased without words disappearing off the page. epub is the standard for this, but it turns out neither Google Docs nor Word can do this satisfactorily–Docs does it, but rather scrappily (for example, Table of Contents isn’t supported). Amazon have their own software for this called Kindle Create. I tried this but abandoned it. There are some glitches (title page has to appear in the ToC!), and apparently it limits what you can do with your books beyond putting them on Amazon.
The solution I went with in the end (following most forum advice online) was just to format everything in Word, then put the docx into Draft2Digital, which does a good job of creating an epub. There are a limited number of templates, I felt a little restricted when choosing how the pages will look, but there weren’t any glaring problems.
I also got ChatGPT to create the cover image for me, which was an adventure. I wanted a picture of a robot serving an old woman brandy, as per the first story in the book. It took about 50 (no exaggeration) goes to goes to get it right. The worst one is below: it’s maddening how close you can get to what you want, but with one or two outrageously glaring errors. The best–well, see the cover of the book!

Draft2Digital also provides a very convenient way to do all the legal stuff and to distribute the book to a lot of sellers. I’d intended to just go with Amazon, but now it’s on about 20 different sites.
I’d planned on giving this away for free, but that wasn’t an option, so it’s as cheap as I could make it. I’m going to do another with previously unpublished stories soon.