This guide is intended to make sure you're ready to start self-hosting. Read through the below information and confirm that you have everything you need before proceeding.
In order to use Cloudflare's Tunnel service, which is how we're going to securely open your Raspberry Pi up to the Internet, you also need to host your domain's DNS records with Cloudflare.
Although this is a fairly easy thing to do, if you already have live DNS records hosted elsewhere, this part of the process can seem like a bit of a waste of time, and I don't entirely disagree with you. Personally, I'm pretty settled on where my domains are setup, and I wasn't a big fan of having to move patiopi.com's DNS over to Cloudflare either, but in the end it was a small price to pay for the convenience of using Cloudflare's Tunnel service.
Cloudflare Tunnels allow someone to access resources within your network without the need for you to open up any ports on your router/firewall, which is a big deal. The "old way" of self-hosting would be to open a port to the world, such as port 80, and then forward that port to your Raspberry Pi. Then on your Raspberry Pi you would have a web server listening on port 80, which would serve up your website to visitors. Although this works, it can be a potential security risk, as if you're not careful you could essentially be opening up your entire network to the world.
The issue with this method is that if someone were to find a vulnerability in your web server, they could potentially exploit it to gain access to another part of your network. Then once they get into that part of your network they find an old printer or a new smart bulb with another vulnerability, and the next thing you know they've taken over your entire network.
I realize this may sound a bit alarmist, but it happens, and not just to self-hosters (though I've seen it happen to multiple self-hosters). Pretty much daily there's another story about a company that's been hacked, and it's usually because of a vulnerability that was exploited. And these are companies that have entire teams of people dedicated to security, so it's not like they're not trying.
This is why Cloudflare Tunnels are so great, they allow you to securely open up resources within your network to the world without the security risk of having to open ports. The only thing that's exposed to the world is the tunnel service itself, and that's behind a whole suite of security tools from Cloudflare.
NOTE: Although you can technically use Cloudflare's Tunnel service without hosting your domain's DNS records with Cloudflare, it requires that you be on a business plan that starts at $200/month, which is a bit much for doing some self-hosting.
If you've read through the above information, you're feeling comfortable, and you have everything you need, it's time to start self-hosting!