The instructions for a 12" block are on post #18 of this thread:
Cooper's finished quilt
I think you need around 2 yards of each of your fabrics. The last couple of these we made used smaller blocks and I think they turned out better. Here are two of them:
Another set of twins - Ellery & Aubrey
You can fold your fabric and play with proportions to get it how you like it to avoid cutting up too much fabric.