Razor-qt is an advanced, easy-to-use, and fast desktop environment based on Qt technologies. It has been tailored for users who value simplicity, speed, and an intuitive interface. Unlike most desktop environments, Razor-qt also works fine with weak machines.
There is a package in the AUR, https://aur.archlinux.org/packages.php?ID=49663 .
Razor-qt will ask you to choose a Window Decorator. Most people use Razor-qt with either KWin or Openbox. You can install either but you can also use Metacity (of GNOME) or any other one.