Sociedad led 2-0 at the interval following an early double from Frenchman Antoine Griezmann.
It was 3-0 in the early stages of the second period when Carlos Vela thumped one into the top corner, before Griezmann completed his hat-trick late on.
Read how it all unfolded in Sports Mole's minute-by-minute live commentary of the action below.
SOCIEDAD: Bravo; C. Martinez, Ansotegi, I. Martinez, Angel; Markel, Pardo, Prieto; Vela, Agirretxe, Griezmann
ELCHE: Tono; Damian, Botia, Lomban, Albacar; Perez, Sanchez; Gil, Coro, Aaron; Manu