Forward Naked Domain

Domain Provider Redirect

If your domain provider lets you redirect your naked domain to the subdomain address (e.g. make example.com redirect to www.example.com) then configure that.

Forward Naked Domain - GoDaddy

Forward Naked Domain - Google Domains

 Instructions: Use a Synthetic Record  Also see Steegle's Instructions

Note that in Google domains forwarding http:/mydomain.com and https://mydomain.com will work.
Examples: http://k8oms.page https://k8oms.page

Alternate Method 

Add an A record of @ (or your naked domain) that points to 174.129.25.170 (a free service from wwwizer.com) from https://www.steegle.com/google-sites/how-to/assign-custom-url-domain-personal