for sbox 2

[Demonik1]

Just download peer to peer on the Garry’s mod workshop then the start multiplayer game will work they just have to be your friend

[bartholemue]

creating a server from gmod doesn't work, and I don't have access to my home network details to create a private server

That's not what I meant. When you start Gmod press new game instead of multiplayer. Find the map and click on it, mess with the settings and press start new game. After it loads, you just invite everyone and boom you have a private game. I would suggest disabling all of your mods before you start though and only activating the important ones. If someone trys to join you with your mods active they will have to download all of them just like a normal server.