Así es, Alex. Se utiliza "estar". Pero "camisa" es femenino y entonces se dice "¿De qué está hecha la camisa?" o, un poco más correctamente "¿De qué material está hecha la camisa?"

That's it correct and well said. You have to use the verb to be (Ser - Estar) and the past participle of the verb "make" (Hecho) A correction: in this case, you have to write "hecha" intead of "hecho" because shirt (camisa) is considered as a female thing so you have to write the verb ending it with an "a". if you have any comfusion with this conrrection, don't take it importance, it is not important learn it yet.

It's very easy Alex. "What is it made of?" in Spanish is "¿De qué está hecho?" and "It's made of..." in Spanish is "Está hecho de..."