I know that we didn't need to be ranked for the previous clash because it was so close to the start of the season, but do we need to be ranked for this clash? I haven't finished my placements but I have a provisional rank and have a clash tier on my team's page.
You can play if you were ranked last season or this season in flex or solo queue.
https://na.leagueoflegends.com/en-us/news/dev/dev-2021-clash-check-in/