So here's how it's done. First I set up my lighting for the scene, set a camera on a tripod and locked the focus, white balance, and exposure. I would be taking 19 exposures and would not be touching the camera in between shots to avoid any chance of misalignment between one frame to the next.
|Base image of just the minimal scene|
The first shot I took was probably the most important of them all and its a shot of the scene minus any models and additional props. After capturing this base exposure I just carried on shooting while holding my floating objects in a different position in the air for each frame. You can see that I'm using a remote trigger to fire the camera and lights and the only other thing I needed to take care of is to try to hold everything with my hands and fingers as much 'behind' the objects as I could, which would make the retouching part quick and easy to carry out.
Once I had my 19 exposures, I simply opened them all in a single a Photoshop document as layers. Making sure my base image of the empty scene was on the bottom layer, I was now able to work on each of the other layers individually and just erase anything I didn't want showing in the final image. Because I was careful of how I held each object while shooting, any retouching I needed to do was minimal.
And there you have it!