I blogged about this last week, and mentioned that I thought it might be better with baker's twine instead of yarn. I couldn't resist trying. And I must say, I love the result.
These are just 8X10 pieces of three-quarter inch thick plywood. I printed out a simple state design and used carbon paper to get it on my plywood. I used some cheap three-quarter inch long nails with about an eighth inch head (that helps to keep the string on the nail) and nailed them about a quarter inch in, spacing them about a quarter inch apart. And then I raided my scrapbook supplies for lots of bakers twine. The secret I learned is to work with the entire spool attached to ensure that you have enough before your cut (it uses a lot twine!).
I do love the yarn look for more fun textured look, but the bakers twine does look more polished to me. Here is one with yarn that I made for a graduating senior student - I love the colors she chose and with yarn, I think it adds more of a young look.