Another way will be to use InfinityFree SSL tool to install SSL cert. Then add the custom domain to CloudFlare. Last step will be to change SSL mode to full or full(strict) within CF. No .htaccess modification will be needed.
For those who find renewing SSL cert every 3 mths a hassle, get a self -signed cert from
https://www.selfsignedcertificate.com/
This method will only work with custom domain.