We have proposed and developed a simple 3D authoring/presentation system for immersive virtual reality environments. Our system enables a user to create and edit presentation content both by using a 2D graphical user interface (GUI) on a PC desktop, and through direct manipulation by hand gestures in an immersive environment. The user can thus enjoy the advantages of both simple GUI operations on the desktop and efficient tuning of 3D layout by direct manipulation. The system exploits various features of 3D visualization including 3D nested structures, 3D graph structures for hyperlinks, and 3D depth for zooming or focus+context visualization. In other words, our system utilizes 3D virtual space to produce effective and interactive 3D presentations in immersive virtual environments.