Pick
out your pattern - make two copies of it.
Pick out your glass.
Cut
out one of the pattern copies, leaving the other one
whole as a reference.
Glue the pattern pieces on the glass.
Cut
the glass
Grind
the edges of the glass pieces if they need it.
Place them on the uncut
pattern copy.
If they don't fit together just right - grind some more
until they do.
Wrap
each piece with copper or brass foil tape.
Solder the pieces together.
The solder will only stick to the metal.