The "Block Sites" category of rules can be used to block access to any website on the Internet. If you create a rule containing a specific website's name in Block Sites, Safari will refuse any connection attempts to such a website.
How to block sites?
On iOS:
Launch 1Blocker;
Go to Safari > Custom > Block Sites;
Tap the arrow in the upper-right corner and choose "New Rule";
Choose a name for your rule (optional) and put the domain. Both variants with and without the "https://" part are valid;
Tap "Save".
On macOS:
Launch 1Blocker;
Go to Custom > Block Sites;
Press the "New Rule" button in the lower-right corner;
Choose a name for your rule (optional) and put the domain. Both variants with and without the "https://" part are valid;
Tap "Save".
If you want to get quick access to a site blocked by 1Blocker, you can load it without content blockers, learn more: Quick access to content blockers in Safari