Hi Tom

I think from your model you will have issues making this into solids , when making jewellery it pays to make simple solid parts and boolean delete any shapes or profiles you need.

If you don't mind me saying I would start with the basic shapes and extrude them as solids

you than then easily delete the curved slot out from the cross



Then use flow to curve the insert into the base, it needs to be .1 or anything wider than the base to boolean delete out cleanly without leaving a messy side wall





cheers
shayne