Translations:Keyboard layout switching/46/en
From Gentoo Wiki
This method is recommended for configurations without desktop environments, in other words just X11 with a window manager. Since Gnome removed the ability to change the Keyboard layouts in GDM using the gnome-control-center, GDM also relies on this method on systems without systemd. Create the 10-keyboard.conf file and configure it with the appropriate keyboard settings. Create the directory /etc/X11/xorg.conf.d if it does not exist.