The original idea was 3 columns with 24 shelves each. She had a lot of paper and thought 72 shelves would be nice. It was going to hang on the wall. Then I was going to box in a few shelves below for holding other supplies. All in all it was going to be 60" across by 48" high with 3 colums of 13" X 13" shelves. It was going to use spoon shelf holders for the paper shelves to sit on. That was the original idea.
So I went shopping and found the wood I needed, and the screws, but when I came across the spoon holders I was a little surprised to see they wanted $5 for a set of 48. It was going to cost about $30 for just the holders, about as much as the wood. So I returned home and found out the neighbor had a unit built by someone and they just routered the shelf grooves. Which was free! Bingo!
So I returned and purchased the wood.
2 - 12" X 8' X 1" pine boards $9 each
1 - 12" X 10' X 1" pine board $12 each
3 - 4' X 8' X .25" hardboard sheets $5 each (Thinnest I could find and they are plenty strong enough)
1 Box of wood screws 2.5" $4 (You only need about 20 screws so this may not be needed)
I cut the 8' boards in half and routered slots approx 3/8" deep every 2" using a 1/4" bit. This was tricky doing the routering without any guides to keep the cuts straght. I'll be honest my lines were a little cricked :) I still don't know if I would rather pay for and use the spoon holders. In the end even my most crooked line was not even visible once the shelves were in place. Anyway if you have a drill but no router then I would just drill the holes ands use the spoons or wood dowls. Your choice.
I cut the 10' board into a 60" piece and a 41" piece. Then I lightly sanded by hand all the cut boards and edges.
I then using a table saw but you can also easily use a circular saw, cut the hardboard into 13.35" x 12.5" almost squares. They are set to be 13" wide plus the room for the grooves to hold them. They are set for 12.5" deep. a 12" wide board is actually 11.5" deep so in order to nat have board sticking out so far I reduced them a little. I also have a .75" X 2" X 3' board behind the shelves to secure them to the wall which gave me a little room behind for the shelves to slide back a little farther.
Part 2 putting it all together -->