It was difficult to do, but what I did was I flattened the clay and started to make it round as well as i could. Then when it was relatively round with an opening in the front, I started the detail in the front. What you are trying to do is to flatten it so when you round it out with will already be hollow. I wouldn't try to make a solid ball and then try to hollow it out.
This is weird, but one of the things you could do to make it easier is to get something out of those small machines at things like supermarkets. The small things that come in bubbles like this (www.gumball.com/images/product… then you can use the capsule! Just cut it with sissors to make it shorter (it would be too long if you didn't) and then form the clay around it~ But you would have to remember to poke a hole at the top so you can attach the wire for the jewel and the necklace chain!~
I hope this helped! If not please feel free to ask me~ :3
I put it on a clear string, then you poke a hole in the top if the necklace so you can string it through After you spray paint it. The jewel is one of the last things to add. You just put a little bit of hot glue in the hole you poked earlier and string the clear string through and let it cool off. Then your done! Hope that helps~~