Dick For a piece like that, consider putting a smaller spot type light from above and behind the piece, probably slightly to the right or left. This will create a very interesting shadow in front which will also give shape to the white base because it will also have a shadow.
then carefully add light to the front to bring out the color and texture of the piece without eliminating the shadow. The ideal way of doing this second light would be a soft box from above but you probably don't own one. A set of 3 translucent panels stacked to make a box would work. The U shaped box would be set over the piece so that it's mostly forward. This wouldn't block the rear light and you could put the other light you now own over the top or even at about 45 degrees and slightly toward the front to illuminate the front of the piece.
I don't have any pierced platters so can't shoot a piece like that but maybe I can set something up in the office today to show you what I'm talking about.