How do I avoid to accidentally decline them...
Generally speaking, the names are pretty obvious: Clan League 16 | Division D - <template name>
You know which templates you are supposed to be playing, so if you get an invite by the CLOT Bot (
https://war.app/Profile?p=3719108305), join those games. If you get invited to a CL game you were not expecting to get invited to, reach out to your clan contact.
For example games, clotpages and stuff, see
https://war.app/Forum/596510-clan-league-15-division-c-official-thread (yes, its my own thread, but i'm only using it cause i still had it bookmarked 🙈)