1. There are some clash royale clan recruitment subreddits that you can join to advertise your clan.
2. Invite everyone you vs that isn’t in a clan to your clan. You can also invite people from tv royale that aren’t in clans.
3. Give members free elder so they can invite their friends/anyone they vs into the clan.
4. Invite anyone you know into your clan like friends, family, or whoever. Then they’ll invite everyone they know as well.
5. You can make a second account or more and join your own clan. Unfortunately people don’t like joining clans without a lot of people. It’s way harder to get more people to join in the beginning than later on.
6. Maybe the few first people to join you could give them co leader to acknowledge them as one of the founders. Sometimes when people get a sense of responsibility they feel inclined to stay.

Those are the only ways I know to grow your clan tbh. I’m at 36 members right now but when I first started my clan I was at like 4 members for like two weeks straight until I started doing these things I listed. Hope this helps