1) Draw a small furnace with a bright open flame at the back of the house so we can see where the glass is blown. Put some finished glass pieces on a bench or a shelf nearby, and add a pile of sand to show what glass is made from, since this spread is about what things are made of.
2) Sketch a little glass-blowing furnace with its flame in the back room of the house. Show finished glass objects resting on a shelf or workbench, and include a heap of sand to represent the raw ingredient for glass because this page explains what things are made of.