Plywood boxes from Monterey Box ship flat and are easy to assemble. They come in four standard sizes - a cube, a long box, a tall box and an box sized for Ikea shelf units. Box tops and custom sizes are available as well.
These boxes are pre-doweled and grooved (for the bottom panel) and have a 4" hand hole cutout. A small bottle of glue, Velcro strap and assembly instructions are included with each box.