Here's a few other distros that i enjoy and that are on the lighter side, even though they're larger than Slitaz.

Personally, i'd look at the usability of a distro first and then the file size, which seems to work out nicely for me with the below distros, since their desktops (e.g. LXDE/LXQt, XFCE) are fully featured and there's a sufficient amount of software for them to be daily drivers.

Puppy Linux: https://puppylinux.com/

Lubuntu: https://lubuntu.net/ (uBlock now seemed to warn me about adware, not sure what's going on)

Xubuntu: https://xubuntu.org/