As a Slackware user, and also having used LFS for a while, I thought that it was Slackware that was closest to LFS, without all the trouble of having to build the base system by hand. Once installed, the system could be extended, if needed, by using software packages from different sources, just like LFS. I did try Arch a while ago and found that Slackware was easier to install than Arch. Here's an analogy: being more of a kit, Arch is an AR-15 of Linux, whereas Slackware is an AK-47: it just works (it never failed me, anyway).