So, with a view to practicing, I got hold of some black foamy stuff, and wrapped it round the end of the flash to focus the light in a narrow field rather than having it spill all over the room.
The flash was then attached to the wireless trigger set to 1/16th power and placed on the floor so it pointed upwards to the space where I wanted to be. I took a couple of test shots to make sure my position and the flash position worked OK (f32 was too dark, f8 let too much ambient light in for the exposurte time I wanted).

Once I was happy with the effect, I then stuck the camera on the tripod, locked the focus just in front of a black tv screen and set the timer. I had a few duff attempts where I hadn’t managed to get myself in the shot, but finally got myself in the right place. The Flash was set to first curtain sync, so as soon as it fired, I slipped out of the shot and then used a keyring torch (one of the cheapy single LED ones) to paint in some swirly light.

Empty promises

Post processing was just a bit of sharpening and a conversion to black and white.
Aperture – F11
Shutter Speed – 10 Seconds
ISO – 100