Can you torch clay instead of putting it in a kiln?

No. Metal clay is being sintered by the torch. Pottery clay has to be vitrified (partially converted to glass in simple terms) and before that the chemically bound water has to be driven off of the clay at around 900F. The process of firing clay includes the term "maturing" which is a measured rise in temperature over time that lets all the clay undergo all the steps from rather soft fragile "dry" clay to hard brittle ceramic. Torching is too fast and uneven to do this.