With the current system, the Guildmaster can allow players of different ranks to invite members to the guild.

So most guilds currently have such a player, usually an officer but not always, put a message in zone chat that explains what their guild is about and what sort of players might be interested and respond to anyone who is interested. If a guild were very interested in recruitment across all time zones, they could simply ask their current membership for people in those different time zones who wanted to take some time to recruit. If they want people to be invited very freely to their guild, they can allow all members to invite their friends and acquaintances and so forth. I've been in guilds that did it both ways.

So until ZOS decides this is a feature they want to implement, that's how guilds handle it in game currently.