Basically Serverless will deploy separate API Gateways for separate services. If you want all of those services behind the same API Gateway you can either deploy that whole API as one service (which leads to lots of code in that one service), or you create a separate API Gateway that you then connect to the different functions deployed independently through serverless, or you have another API Gateway that proxies requests to the actual services that are running behind the scenes.
At the moment this is a bit cumbersome and we have to find better ways to do this in the future.