My brother designed this set-up and made the plans for it. I cut it out of 1/8" clear acrylic with a laser cutter, but he made his out of wood. You don't need a laser to make it, but I made mine at Techshop!
During game play, he came up with the perfect order for organizing your cards, based on what they're used for:
Wood, Brick, Wool, Grain, Ore, Settlement
Why this order? Because:
wood + brick = road
wood + brick + wool + grain = settlement
grain + ore = city
wool + grain + ore = settlement card
So I decided to design some emblems to etch into each card slot as a reminder.
Once I'd assembled all the files and printed it out, it was super easy to assemble. Everything slots together perfectly (when using 1/8" thick material), and can be glued in place. This card holder is even large enough to accommodate expansion packs!