@andygrat, I would rather suggest to try 1-click Siteground solution first. When you add CloudFlare from within Siteground control panel, CloudFlare will fetch all DNS records of your domain and subdomains on it. Whereas, when you manually configure, CloudFlare fetches DNS records externally and may sometimes miss DNS records of the subdomains and you may have to add them separately.
Anyways, once the domain has been added to CloudFlare…DNS records fetched… and the Nameservers at your Domain Registrar updated with your CloudFlare Nameservers you’ll configure as follows for www to non-www redirection:
As STEP 1, ensure that the naked domain is pointing to your SIteGround IP using an A record. It would look like this under CloudFlare DNS section:
[A] [mydomain.com] [points to 220.127.116.11] [Automatic] [Orange Cloud]
… and the www subdomain be CNAMEd to Naked domain:
[CNAME] [www] [is an alias of mydomain.com] [Automatic] [Orange Cloud]
As STEP 2, you would use the following Page Rule under Page Rules section for redirection:
If Url matches: http://www.mydomain.com/*
Forwarding URL with 302 Redirect
That’s all! Hope this clarifies.
Or, you could hire someone to do the stuff for you https://www.fiverr.com/search/gigs?query=cloudflare