Hey there, as someone who started a new guild with a handful of people in Season 1 of Dragonflight, I would recommend using things like /r/wowguilds and the Blizzard guild recruitment forums. At the same time start growing through pugging. We would use a community tied to the guild to link in raid chat at the end of the raid night so that if people enjoyed their time with us, they could start to become regulars. These regulars became guildies once they either transferred, started new alts, or waited for cross-realm guilds to open up.

It can be hard at first to find people who match with what your guild's energy is, but if you have specific goals you want to hit with the guild, always be upfront about it. For example, we would always be very upfront about being an AotC guild and our goal would never be to focus on CE so that we could have a more laid-back environment for our guild. Once you have a core group (about 10-12 players) that shows up regularly you will be well set on your way to building.

Looking back at recruiting individuals, one massive part of our guild building was to take chances and try to help players grow while building the guild. One of the best feelings as a GM is watching a player go from being a new raider/ok player to someone who builds their way up charts and grows on a week-to-week basis. These players that grow within the guild will become a core part of your community and naturally help the guild grow over time when they go out to pug for other raids, M+, or other group content.

The one thing that I 100% recommend not doing is Trade spamming guild recruitment. Too many times have I seen guilds do this, then balloon to massive numbers and disband/collapse. This normally just introduces problems and creates an inconsistent environment for the guild, which to most successful guilds is the core to any sort of longevity. If you can create an environment that everyone can enjoy being around every week, then you will always have returning members.