Glass Vessels mimic the look of finely blown glass.  The detailed design comes about from creating a ‘blank’ or 2-dimensional piece of glass laid out in various designs.  The design can be carefully laid out or can even come about from a mixture of glasses randomly placed within the kiln and brought up to 1480 degrees.  
That ‘blank’ is then elevated on a specially cut mold with the center portion removed and, for several hours, as the heat in the kiln is slowly raised to 1200 degrees and held, the glass will soften and drop through the opening.  Additional cold-working can be done to remove the rim to create a vessel that looks like a piece of carefully blown glass.