I have never found felt cords and balls as simple and easy to make as everyone else!  When Sigrid and Ingrid Bannier were in Ireland at the end of November I asked Sigrid how she was able to make her cords so strong and even, here is the method that she uses as I understand it.  It certainly works for me!!  Lay out a horizontal line of wool to whatever depth you want (depending on the thickness of cord required) with all the fibres running in a vertical direction, as most of us would do anyway when making cords.  The big difference is in the rolling, if you are right handed start at the left hand end, if left handed start at the right hand side.  Roll the fibres on the diagonal instead of in the normal straight line.  It is a tiny bit more difficult when visualising it but quite simple to do, rolling in this way really allows the fibres to form a tight cord.  Dry roll for a minute or so, wet lightly with warm water and olive oil soap, roll some more and then wet out as required.  Keep rolling and dunking in hot soapy water until the cords are to your satisfaction then rinse and leave to dry.  If you want to have curly cords just shape the wet rolls around a metal knitting needle, tie with cotton thread to secure and place in the oven on low to dry.  If you check out my Flickr images I have a blue necklace in the necklace set that I curled using this method.