Scott, Since no one responded to your question I will comment. Basic ribbon forms are made by turning two or more identical compound stave, bottomless bowls with a slope or cone angle of 45 degrees. The bowls are then bandsawed into halves (or even quarters) and reassembled into more interesting shapes. Beyond that one can use multiple bowl sizes and multiple slope angles. The possibilities are endless and truly mind boggling. For an excellent tutorial on this and many aspects of segmented and stave turning suggest purchase of Malcolm's "The Art of Segmented Woodturning".