End-to-end Joining 1/2" Stock

I have some 5ft long x 5" wide x 1/2" thick planks that I want to joint end-to-end to make a total of 8' boards. I'm struggling to find a correct joint to do this.

The plank will be decorative only and will not support any weight, but will be hung horizontally at both ends only, so I don't want it to collapse under its own weight.