My DH, who's not normally good at wood-working, made me a beautiful rack by taking a short board from the cellar, buying a 1x4 (I think), cutting it, and screwing/gluing it to the base board to make "dividers"'that hold a few rulers each. It's lovely and was fairly cheap and easy to make with really basic tools. The one I kept seeing online was a mere 4" deep and had slots made with a router. Without a router, he went to building up a few "curbs," and it looks good and works beautifully.
hugs,
Charlotte