Even with Starkiller Base at its disposal, The First Order would have kept other secret locations, and on one of those is where Snoke would maintain a low profile and keep track of the organization’s operations from afar.
Much like how the first Death Star’s destruction wiped out a significant portion of the Empire forces in A New Hope, The First Order lost a lot of its people when Poe Dameron destroyed Starkiller Base in The Force Awakens.
While it isn’t 100% guaranteed that the “Mars with snow” world will be a First Order stronghold in The Last Jedi, it would make sense.
However, Kylo Ren and Hux were able to get off it just in time.