How hard is it to create a map?

It depends on how far you want to go, and there are two tools for two levels of ambition.

The built-in map editor, no code required

From inside your space, with an admin or editor tag, open the map editor in the action bar. You can place objects and furniture, add interactive objects such as a computer that opens a website, define areas like meeting rooms, exits and entries, and edit in real time with several people at once. Most teams never need anything else, and this takes minutes rather than days.

Tiled, for full control

Tiled is a free offline editor used to draw floors and walls, build a map from scratch and add scripts. It is more powerful and asks for some design skill and patience. If it is your first map, start small and simple, and count one to two days.

See the map building documentation to choose between the two, follow the Starter Kit and download Tiled. Video tutorials are also available.