Descriptive Worldbuilding

When I was writing The Duchess, Her Maid, The Groom & Their Lover, I was doing a lot of my worldbuilding on the spot, whenever I felt something was needed.I do think about aspects of the world before I begin writing, but probably just as much comes along in the middle, or during revisions, when I suddenly realize, "I never described this room, and that would set the scene better."If I'm in a