This is the map from The First Fantasy Campaign, that the video mentions. It is the Blackmoor regional setting.
It is less visible here, but in the Elven Forest there is an Elven city called Ringo Hall. The Elven Forest is on a peninsula.
The town of Blackmoor is a coastal town on the southwest corner of this peninsula. Across the south of the map is swampy wetlands, that are ambiguously land or water.
This Blackmoor regional setting exists in the Greyhawk Campaign Setting, to the far north on planet Oerth. Here, the entire region is called Blackmoor, the Archbarony of Blackmoor. The archbarony is named after the old Blackmoor town, but the current capital moved to the new city of Dantredun.
Here is the Archbarony of Blackmoor, the Blackmoor regional setting on the famous Darlene map, for the Greyhawk setting. It is a stylized approximation that simplifies the details.
In red, I added the corresponding locations of the old Blackmoor town, essentially a fishing village on the SW corner of the peninsula. I also added the location of the Elven city of Ringo Hall.
Note, the "Ruins" that are in the Archbarony of Blackmoor appear to be the ruins of Ringo Hall in the Elven Forest.
The town of Blackmoor itself appears to still exist, albeit it is small and unnoted on this map. To its south are the wetlands. Interestingly to the north of the peninsula, much of the "Sinking Land" has sunk beneath the waves. But most of ths region is shallow wetlands, so different maps might decide what is land and what is water differently.
(If placing the Blackmoor regional setting in the Forgotten Realms planet of Toril, I would locate it somewhere in the subcontinent of Anchorome, at its north coast.)