Jeanne - Be sure you try to find some "furniture" pallets as they already have the little boxes built in the pallet. I love mine!
It's funny, because I planted 14 plants in those little boxes and all but 1 plant is still alive over a year later! I really anticipated replanted the herbs every year, but that has not been necessary. Amazing how they can grow with so little root room. Obviously they must be a bit invasive to be so tough!
I would love to see photos of when you build yours! Please do post some pictures.