Point your Cloudflare domain to Webflow
When setting up your domain with Cloudflare, be sure to switch the orange cloud under status to just DNS (greyed out).
Some DNS providers are limited in the configurations they provide (such as the one A Record limit). As an alternative, you can point your custom domain to a third-party DNS provider (like Cloudflare which offers a free option).
Using Cloudflare, all you need to do is make sure your NS records from within your registrar are pointing to your Cloudflare account for your custom domain. Within Cloudflare you'll then setup a CNAME for www subdomain NAME record pointing to proxy-ssl.webflow.com and a CNAME record for your root domain NAME record pointing to proxy-ssl.webflow.com.
Be be sure to click on the orange cloud icons to set them to DNS Only. Set your TTL to 2 minutes and in your Webflow site settings, add your custom domains, turn on SSL hosting, and set either domain as your default domain. Publish your site to your custom domain.
It can take up to 48 hours for your DNS settings to fully propagate.