I bought a 2' x 5' piece of 16 guage steel ($30)and put it on a workbench that I built a long time ago (solid core door for flat worksurface).
I then ordered about sixty 1" x 1" latch magnets from magnetsource ($ 0.65 ea). These magnets hold your work tight and square.
I will never go back to pins again, this thing is the best thing you can use for building.