Theatrical thursday #14 Hand moulding

I'm making a rough hand/arm mould to have something to practice sculpting on. The book I am reading quite clearly suggested to always cast half if you only need half. With an arm, especially my thin, flat. Not a good idea.
But I didn't realise that before after the mould was made, so I extended the edges with airdrying clay and mod podge. And now I'm making a plaster picece of it. For next casting I'll make sure to do my entire arm, it would be a lot easier to fill with plaster.