Now you can easily install pure arch linux from my Arch Live Linux with Calam-Arch-Installer through video instructions, following the steps.
Install Legacy-Bios or UEFI,
Support Luks Yes
There are also 9 selectable graphical environments for installation, Xfce, Gnome, Plasma,Cinnamon, Budgie, Openbox, I3, Mate, Deepin
Good Luck!