If you started from Linux Mint a year ago, I'd say that going directly to Arch could be "too big" to do it in one step (generally speaking).
Arch has good documentation, but it still requires some learning curve. Moreover, being a rolling-release distro, you might find yourself facing some problem that would need some particular knowledge level to be resolved.
This applies in general to every OS, but for Arch in particular, some "extra" knowledge might be a recommended requirement at some point or another.
Slackware (not Salix) might also be a "too big" jump to do in just one step.
So, starting from Mint, you could try / test several stepS, even in parallel (with multiboot installation or in Virtual environments).
One possible 'lighter" path could be LMDE, which is very similar to Mint but uses a semi-rolling release cycle. Or SwiftLinux, or SolusOS.
In parallel, familiarize yourself with one of the many editions of Salix. For an average-knowledge user, you will have dependencies resolution, plenty of packages already out-of-the-box and many more to download and add, without “thinking” about dependencies.
In the mean time, read The Salix Startup Guide, part of The Salix Wiki pages.
From one of the "easier" Salix editions, once you are comfortable with it, you could then try installing a Basic Salix (instead of the Full Installation) or even Salix Core. Or try Salix Fluxbox or Salix Ratpoison editions. Play with adding more than one Desktop Environment to your Salix OS; or adding some customization; or solving something "by hand"; or improving...
After that, you could try Slackel, which is a rolling release mix of Salix tools, latest KDE and "Slackware current" (as oppose to being based on Slackware 13.37, as Salix 13.37 is).
All these experiences can give you more knowledge, distributed in more gradual steps, while still having a working OS.
At some time you then could try Arch in parallel to one or more of the mentioned options, building "your" Arch and learning about its peculiarities, having experienced other "easier" rolling-release distros and Salix Core installation.
Then of course nothing can stop you from adding Slackware itself to the mix.
Obviously, YMMV, and what I wrote here are only very general ideas / possibilities on how to gradually increase both in knowledge and experience, while still having a working OS.
As mentioned, reading the respective wiki pages should also help you.