I found the plans here:
and altered them slightly for my own means.
Total cost is around $20.
Step 1: Measure it out
I copied and blew up the dimensions template, printed it out, and traced it onto the board to make the first piece that would act as the template for the rest of them. You could also just measure it out by hand on the board as well.
Step 2: Drill the holes and cut them out
In total, I measured and cut out 12 of these holders and cut them out with my jigsaw, sanding each down to a 120 grit finish (doesn't have to be perfectly smooth, just sans splinters with no sharp edges).
Step 3: Measure out the placements and pilot drill
I used 1-1/4" wood screws to attach the holders to the board, so I drilled 3/16" pilot holes (1/8" works too), spaced symmetrically 1-1/2" apart on each line of the zig-zag. To be on the safe side, I counter-bored the holes on the back of the board (1/4" bit, 1/4" deep), so that there wouldn't be any chance of the wood cracking.
I then clamped each holder individually on top of one of the lines, with a dab of wood glue in the middle, and drilled the pilot holes through the back of the board about 1/2" into the holder. After the pilot holes, I screwed the wood screws into the two holes.
I then did the same thing to the rest of the holders, starting from one end to the other.