Let me throw in my 2 cents worth. As I understand it, segmentation is typically made from one piece of wood. As you cut the pieces the grain will be running in the same direction. You will do some sanding of the edges and then you finish the pieces using stain, paint, dye, etc. You reassemble the pieces and glue it together. When you do an intarsia piece, you most likely will use several different wood pieces. You try and take advantage of the grain direction, color of the wood, and grain pattern to give the finished affect. Then you cut the individual pieces, shape/sand them for affect. You normally do not use anything but a clear finish on the final piece. JGR instructs to finish the pieces before final assembly. That eliminates trapping finish between the pieces and catching dust etc.