r/CloudFlare: Stuck with "Flexible" SSL encryption

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This article archives a conversation, which took place in a subreddit post (original source linked below) and to which I contributed a solution or answer (with the u/MasterofSynapse handle), in a Q&A format.

Original Reddit post: https://www.reddit.com/r/CloudFlare/comments/xl7djq/stuck_with_flexible_ssl_encryption/

Question

Followed a simple youtube video on how to connect a website to cloudflare (by changing dns).

Everything went perfectly, however I seem to only be able to use "Flexible" SSL encryption (which works, my website shows "Connection is secure" lock icon).

I'm aware that in order to use "Full" SSL encryption, I need to go to: "SSL/TLS -> Origin Server", then generate a certificate and install it in my site managment platform.

Whenever I try to install the certificate I just generated, I get this error in my site managment platform: "Certificate and common name don't match".

I double checked if my website url matches the one when generating a certificate and it does.

It would be awesome If someone could point me in the right direction with this.

Answer

You dont have to use the Cloudflare provided cert, with Full, any certificate, even self-signed, suffices. With Full (strict) you need either the CF origin cert or another trusted cert, like Lets Encrypt.