A view of the locking mechanism
A small hole should be drilled in the hot/cold shoe to accommodate the locking pin of a Speedlight otherwise the Speedlight flash will most definitely slip off at some point.
I slightly modified this particular bracket by shortening the base plate by an inch or so, a small piece of plastic was glued onto the base plate in order to close the end and to prevent a loose camera from accidentally sliding off. This rectangular plastic piece can also be drilled and used as an anchor point to fix a hand strap.
Mounting the Speedlight flash off camera also means that the pop-up flash can be used to trigger the Speedlight and being able to hold the camera unit with the left or the right-hand makes life much easier when swapping accessories or altering the setup. The Sunpak GP-04 camera/flash bracket was not very expensive, I bought mine for £15.00. (now on eBay for £17.50)
In the field, ball heads are an issue when it comes to macro photography, most if not all are incapable of holding a flash unit at the correct set angle for very long, all of the devices I've seen and the few I've used are either inadequate or impracticable, most are too flimsy. The adjustable locking elbow device I'm currently using is made from plastic and was stripped and adapted from the top of a cheap lightweight monopod, although not 100% perfect for the task it'll do until I find or make something better. Potentially there's a huge market for a simple, small, strong, compact well made adjustable device or even a solid rigid device set at an angle suitable for holding a tilted Speedlight for macro photography either on or off camera.
A flash bracket is ideal for longer or heavier lenses that have a tripod mounting collar as the lens can be directly attached to the camera bracket itself ensuring that the weight of a long lens is not putting pressure on the camera's lens mount.
New (old stock) Sunpak GP-04 currently advertised on eBay for £17.50