In flashbacks or narrative exposition, we’d learn how he found and groomed Kylo.
Kylo would talk more and more about Snoke’s elaborate backstory.
Then we’d get a Snoke origin movie which shows him moving about throughout the history of the empire and before, up to its fall, and the creation of the First Order. It would sweep over millenia with the development of Snoke, leading up to the point where he finds and grooms Kylo. The nefarious thing about this origin story would be how he would have silently changed things all along, while individual participants would not have known how they would have been guided.
Then Snoke wouldn’t go out like a punk in Last Jedi: it would have had to have been an engineered betrayal by Kylo which reveals how powerful and clever Kylo is to pull it off.