If you have a router, you can port forward it, after port forwarding it, Run ur "Server Software" and it will appear in the Classicube.net Server list
This server list. (Please view the image)
If you don't have a router, i recommend you to ask an Hoster, like Kamino. (Note: You can contact him in Discord. If you are underage to get in Discord, then you can find him in-game, If you aren't underage, then Click here to enter Discord, I recommend you Download the Discord Apk (or Desktop client) because the web client is a bit laggy, bad, etc).
Or, just Click here to request for a eddynetweb hosting. You know what i mean. Eddynetweb accepted many people, but i don't know why my request is being denied.
It's impossible creating a server without Port forwarding it. If you port forward a Classicube Server, it will appear in the server list and everyone can connect.
Also, You can share your IPv4 address and use MCGalaxy to host. (Reply from Rubiktor012).