I ordered the set which includes the book, ruler and circle templates for all of the compasses and centers. The book explains everything in great detail. Robin recommends that you "practice in a block size between 12" and 18." Robin uses the 18" block in the instructions for you to follow. I did make a 10" size block because I had fat quarters that I wanted to use. She uses the length of the fabric, 42", for the larger blocks.
I made the center circle by ironing under the edges and sewing the edges because I could not find any fusible interfacing. Thus the not so round center. I will try to do the larger compass and post a photo of it. I will have to go and purchase some fusible interfacing ASAP.
I must say that it was fairly easy to do. My only concern is that you have to be careful making the cuts for each "wing" or you will make an error. I like to do faster projects (I am easily bored) but this is a beautiful block so I had better slow down. Maybe I will finish the blocks faster once I am used to all of the cutting that has to be done. The book has great illustrations to make this block.