A Sewing Question For You Sewing Experts

I have a sewing question,What my question is.. I want to make the above figurines into pincushions.. I'm a sewer wanna be , Not by any means a learned sewer(expert) (I will get there one day though stitch by stitch )...How do I make a round bottom to come up and around the base and fit snuggly ? Hope some one can help me.. Do I make a circle for the bottom and then gather fabric to attach to it?? Should I place card board at the bottom??, Do you think these figurines are wron to use as pincushions?Meaning their shape? I was thinking of those antique half doll pincushions?

Thanks so much Sherrie