There are two primary processes I use to cast my glass sculptures:

pate de verre and lost-wax kilncasting.

Pate de verre, meaning glass paste, is essentially a method of packing granules of glass (frit) into a mold before it is fired.  This technique dates back to ancient Egyptian times but is more well known by its current name due to a number of French artists that revived its use about a century ago.

I form many of my castings, including the glass leaves, with this technique because it allows me to carefully control the thickness of the casting and experiment with creating thin and lacey details.  The pate de verre method I use also results in two different surfaces: a shiny reflective side, formed closer to the heat, and a matte surface which was formed against the walls of the mold.

Lost-wax is a method common with casting many materials including metals.  It requires that you create a wax version of what you would like your final object to look like.  Once the wax is complete sprues (wax funnels) are attached and it is entirely encased in a plaster and silica mold material.  When the mold is complete it is then steamed out so that all the wax runs out and a hollow cavity remains.  The mold is flipped upside down, placed in kiln, and cold chunks of glass are placed in the sprues (funnels).  When the kiln is hot enough, the glass melts down into the dress shaped cavity.  After the kiln and mold have been carefully brought back to room temperature the mold material is broken away to reveal the glass casting.