This video demonstrates the map creation process for King's Crook using the Dungeon Editor (dedit) that comes bundled with the game on the itch download page (https://kingscrook.itch.io/kings-crook)
This video is sped up 4x.
King's Crook Discord Server: / discord
King's Crook (and its tools like this and the model editor) are written from scratch in C with no 3rd party libraries and no floating point types.