You can try using # du -h -d 1 / to locate the largest directory under /. Once you've located the largest directory, replace / with that directory. Repeat that until you find the culprit (if there is a single large directory).
EDIT (2024-07-22T19:34Z): As suggested by @DarkThoughts@fedia.io, you can also use a program like Filelight, which provides a visual and more comprehensive breakdown of the sizes of directories.
Ah, I see. Just be aware that any additional file size when you get to the stage you can install KDE is pretty much considered the "bloat" part of installs, meaning you only make arch as bloated as you want after that. I like filelight in KDE https://apps.kde.org/filelight/
Whoops! You are correct — I have updated the original comment. I'm not sure why I wrote df instead of du. This is a good example of why one should always be wary of blindly copying commands 😜 It begins to teeter on being potentially disastrous if I had instead wrote dd.