Welcome to the Airtable Community!
Short (not entirely correct) answer to your question: You can’t.
Bases showcased in the Airtable Universe are “packaged” in a very attractive way that includes what I think you’re calling a “main menu”. That packaging is a webpage frame that contains the base. If you copy one of those bases to your own workspace, you will see that that beautiful frame does not come with it.
I said my first answer isn’t entirely correct because, if Airtable’s folks could do it in the Universe, obviously, it can be done. But it’s not done by Airtable. To accomplish something similar, you need to create a web page yourself and embed the base. Create links in your web page to different views. Won’t say more than that here. Might or might not be your cup of tea.