When I started Cloudflare was number one in solution to security and CDN solution. Even pay plan is better than other competition on planet. It was goal and with increased usage I found some hard corners. In free plan I get option that enable new hosting to be connected - "Origin Certificates"
This add layer of protection and give Netlify certificate that they need.
Before You start:
Remember to create DNS zone on Netlify for branch deployments as we use dns from other company.
How to apply with images and comments: https://blog.millerti.me/2019/01/20/using-cloudflare-ssl-certificates-with-your-netlify-site/
You can use Netlify CLI to deploy and new added "--alias" support branching.
Have a nice day :)