I do a kind of drill down then build up thing - world map, nation map at ca 8 or 10 miles/hex, then often a low level map at 2 miles/hex. I seed the area around the PCs with adventures/encounters in more or less concentric circles of generally ascending difficulty/challenge. I use the system's encounter tables to help fill in blanks.
One big thing I do is focus a lot on major NPCs; something a lot of hexcrawl design stuff ignores. But the NPCs are often the most dynamic element.
Once enough material is created, I make a rumour table, usually for the local area, usually reviewed monthly. A D6 table works well IME. Whenever the PCs move to a new locale I'll look to make a new rumour table.
So eg for my Primeval Thule Mini Six game
https://simonsprimevalthule.blogspot.com/2020/01/the-valley-of-scorn-palace-of-silver.htmlInitial rumour table for Orelustrah based off the one in B3:
Rumours - Gulluvia, ca M1 2215 AR
1. A fierce young female fighter called Aliegha has been seen in a few of the neighbouring villages. Many folks say that she carries a sword of ruby and is accompanied by two dwarves and a cleric. Some believe that she might be a descendant of the Silver Princess.
2. The evil Baroness of Gulluvia, Lady D'hmis, has offered a reward to anyone who can bring to her the ruby known as My Lady's Heart. Lady D'hmis claims to be the heir to the treasure as she is the only living descendant of the Silver Princess.
3. Strange beings have been seen emerging from the Scorned Valley to raid Gulluvia. These creatures, say survivors, have three heads, three arms and three legs. So far five people have been killed by the horrible beasts. Farmers complain that their cattle, chickens and other farm animals keep disappearing, and they are blaming the disappearances on these creatures.
4. A rich treasure is hidden in the Palace of the Silver Princess. This treasure is said to be even more valuable than My Lady's Heart.
5. Lady Argenta is still alive, and living with a band of fellow elves that rescued her from the warrior in silver and blue armor. It is said that she is still as fair as she was nearly 500 years ago.
6. A great priest called Cathrandamus is roaming the country aiding the sick and defending the just. It is said that he cares not for riches, but only for spiritual gain.
7. Half of the palace was destroyed by one of Argenta's magic users when he accidentally mixed the wrong magical components together.
Current rumour table for Thiria Keep/Barony of Tallas:
1. A sorcerous tower on Sinking Isle holds a diamond as big as a man's head.
2. Cultists have been raiding the road between Tallas and Thiria in service to a Chaotic god.
3. The Licheway of the old Sandlanders west of Skyreach Tower has been attracting adventurers in search of treasure, but sinister Deep Ones have been seen in the seas offshore.
4. They say the Sorcerer Tizun Thane is dead, and now strange Night Things have been emerging from his mansion-fortress in the mountains, beyond the Wilds of Chendu-Skar. The villages south of the Tith River are in terror, and Lord Borealis of Tallas has offered a reward to halt their depredations.
5. Veshni Ural the Queen of Nith seeks heroes to find the Lost City of Cynadacea, home of her royal Atlantean ancestors, long believed lost beneath the Tjokren ice.
6. The High Priest of Nergal in Nith has been found dead - drained of blood!
Whenever the PCs talk to NPCs they are likely to pick up rumours, selected or rolled randomly.