Like my LED pin-bending jig, this was one other area that I didn't blatantly copy someone else's work. :) Most folks build a layer at a time with two directions of wire tying the anodes together, then stack the layers vertically. To accomplish uniformity, they drill directly into a sheet of wood to make a jig for soldering. I knew that if I went the vertical layer route, I would wind up with a bad LED smack in the middle of the bottom row (for no reason aside from bad luck). I had been brainstorming on ways to turn the rows into vertical sheets. I came across Vespine's cube http://v3spin.blogspot.com/ where pretty much the exact thing was done. Seeing it that way sealed the deal for me. I still liked the idea of laying out an entire layer at a time in some sort of jig, so I cut 81 little half-inch blocks and drilled a 3/16 hole into each. I glued them down as nice and square as I could make them (I chose to space my LED's 1.75" apart). So this rotated all of my LED holes into a position that would let me solder up a full vertical "blade" as Vespine aptly calls them and help keep things consistent throughout the soldering process. I hope.