Coal tar is a thick black liquid produced during the destructive distillation of coal. It is a complex mixture of hundreds of compounds, primarily hydrocarbons. These compounds are the raw materials (feedstocks) for producing many synthetic products.

Among the options:

• Clay and leather are natural materials, not synthetic products from coal tar.
• Cellulose is a natural polymer found in plants.
• Naphthalene balls are made from naphthalene ($C_{10}{H}_8$), a specific compound isolated from coal tar.

Final answer: naphthalene balls.