Planked shield without reenforcement

[cmmcgarr]

It looked to me like the oval shields from Dura Europos were made just from butted planks without a reenforcement to hold the planks together (such as how viking shields are supposed to have three strips of iron across the back). How would the shield be held together without these reenforcements? Does anyone have any experience making a shield like this, or have idea as to how I could do this?