Creating a lobby in Godus is as simple as clicking this tower. The Steam overlay will then show up, you can invite a friend from here but you can also close it.

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After you have closed the Steam overlay, you should see up your screen a text similar to the picture, in red is the lobby id you have created silently. After this you are all set to receive Steam invites. If a friend or non-friend follow thesection of this guide he will send you and invite to start a new game