Take two cheap wired based headbands that have a knit like covering. They are often sold in packs of 4 at your local drug store. The wire base will allow you to manipulate the shape of the headband and the knit exterior will allow you to sew them together. I used a combo of sewing through the knit exterior and wrapping the thread around to ensure it was a strong connection.
Use your child's head to size. Sew together as shown in the picture. After sewn together I pulled and manipulated the headbands to make it look more circular.
Have ready: long pieces of ribbon and tulle cut and ready to go for the back of the fairy crown. Take a really long piece of ribbon (I am sorry I didn't measure mine.) I used satin ribbon. Starting in what will be the back of the fairy crown. Leave a long tail - you will be tying it off at this point. Hold the tail tightly. Start wrapping ribbon around. Overlapping as you go. Make sure it is tight and neat. I ended up holding the tail between my knees once I had wrapped a few inches. Wrap all the way around until you get to the tail piece. Tie together once - pull tightly. Place the cut tulle and ribbon in center of knot and tie again - securing tulle and ribbon in place. Tie a bow - double knot it so it doesn't come loose. You could put a dab of hot glue there too. If using satin ribbon you can slightly melt edges of ribbon by holding end briefly above a lighter. Do this in a well ventilated area as I don't know that it is good to do this. Please be careful! What this does is it ensures the ends won't unravel. If using grosgrain ribbon - use fray check.
You could jazz it up even more by adding silk flowers or leaves. The color combinations are endless. I chose red for Christmas but can't wait to try it in a rainbow of colors!
This would also be beautiful done in white for the little ones who like playing bride!