This is a real simple thing, a small platform raised off the main bench with a 6" pipe nipple and flanges. It is just a bit bigger than the boxes I work on. It gives a flat surface that can be clamped down from a couple of different sides.
I made a similar work station by screwing a piece of plywood onto a piece of 2X2 and clamp it into my bench vise when needed. Very handy and I use it most of the time as my bench tends to be very cluttered. It's visible just to the right of the tool box behind one of my other projects.