How was the amber spyglass made in the novel, The Amber Spyglass?

Mary Malone makes the amber spyglass out of a lacquer made from the sap of seed-pod trees while in the world of the Mulefa. She cuts the sheet in half and creates two lenses. Through two lenses, she can see Dust. The Mulefa make a tube for the two lenses and thereby create a spyglass.