First clone the repository with
git clone https://github.com/kalehmann/unlocked-client.git
Then create the package (as non root user) with
cd unlocked-client/packaging/aur
makepkg
Next install the package as root with
pacman -U <path-to-the-package>
After that configure the unlocked-client by editing
/etc/unlocked/unlocked.conf and finally enable the socket inside the
initramfs with
systemctl enable [email protected]