There's one method I use, picked up from MobileRead member
jjw (not sure if I spelt that right). I'm not sure that it's better, and it certainly is longer, but the advantage is that everything is arranged very neatly. I like having a TOC, having names to those chapters, and not having separate volumes clutter up the library.
To summarise: I have all the JPG or PNG files of each chapter archived in CBZ or CBR, so 01.cbr, 02.cbr ... 25.cbr, if there are twenty-five chapters. They should all be in the same directory. I use the command line to print the contents of this directory into a text file (quicker than typing it all out), so
I can do this. Once that's done, I dump all the directory contents into the one CBC file, then let Calibre process and automate everything. It usually does a good job with splitting images, resizing them, etc.
The result is a huge EPUB, but one that's quick to load because of the frequent page splits. The TOC is multi-level, the top level showing a list of chapters, and drilling down shows the pages in each chapter. As an example, the manga series I've converted into EPUB is 25 chapters, 200 MB, with a multi-level TOC.