The best way to block an IP address from accessing your website is to add the IP address to your server's firewall. This will prevent the IP address from accessing your website, and you can also block the IP address permanently if you wish. Additionally, you can also use a third-party service such as CloudFlare to help block the IP address from accessing your website. This is a more comprehensive solution, as it will monitor your website for malicious activity and block any IP addresses associated with it.