In Like Flynn, and his use of the An Echo Resounding sourcebook, I've taken a similar approach to the corner of my big, partially sketched out campaign world for the PCs to explore if they survive the current castle raid.
It's in the south-west of the main campaign land, with a Kingdom (Celise) formed by a people fleeing an Ancient Evil from the north-east of the main campaign land a few hundred years ago, the lands of the Drakkan Barbarians, a cheerful and honest people, with bloody tendencies, and the Dread Kopesh Marshes, home of many interesting things.
That description was all I had before this endeavour, along with a portion of a map some 5 cm wide. Thanks to the process in the Echo book, and the marvels of printing at 400% magnification, I have a map and a series of locations that gives the area issues, complexities and hooks that I never knew existed.
Here's the basic ideas I had, pre-embellishment;
The Stable Empire - That's Celise, for which I have a reasonable history, stolen from a previous campaign setting. There's Machiavellian Politics, the Queen's Spy Network, who are ruthless and efficient in combating both the Blood Cultists and any perceived faults of the King's Guard, and a number of shunned areas of monsters and Ancient Ruins.
The Innocent Savages - The Drakkan have supplied the odd PC in the past - tall, blond, tanned, muscles, with a general good-natured humour that remains even when busting skulls. Their traditional land, between a towering mountain range and the coast, is rich in herbal and sorcerous produce, but they object to strangers coming in and stealing their stuff.
The Dour Highlanders - not really faux-Scottish, but upstream of the Kopesh is the Yar River, and the northern side is occupied by the smoky hamlets of Pelidoth, whose populace herds goats, burns peat, cuts timber and scowls at passers-by.
The Lush Wasteland - south of the Yar, the savannah and scattered forest clumps are green, well watered, and littered with the bones of would-be settlers. Mainly on account of the goblin warbands, xenophobic elves and undead infested ruins.
The Coastal Cities - almost peripheral to this map, they form the escape to the north, along the coastline of the Pale Sea. Each independent, some trade havens, some Ports of Thieves, each potentially deadly. That's where the big markets and serious thieves guilds are...
The updated and investigated locations later...