Start with any shape piece of wood
Draw a shape, design, or words that you want to be the "picture" of your piece. The more simple, the easier it will be.
Stain or paint your wood. I used a combination of both to get the color I wanted
Here comes the long part. Nail in nails close to each other following the line you drew previously. I added more. Then I painted a clear coat to make it look more finished
Next you're going to take your string and connect the nails kinda like connect he dots. You can do them in any pattern you want. This one took a long time.
Finally cut the extra strings and you got your finished product!
Here's another one I made using a different technique with the string. Enjoy!