Add stack:
SW1
int stack-p 0/1
port int g0/0/12 enable
stack slot 0 priority 200
SW2
int stack-p 0/2
port int g0/0/11 enable
quit
stack slot 0 renumber 1
save & reboot, and then plug stack cable
Delete stack:
SW1
int stack-p 0/1
shut int g0/0/12
undo port int g0/0/12 enable
stack slot 0 priority 100
SW2
int stack-p 1/2
shut int g1/0/11
undo port int g1/0/11 enable
quit
stack slot 1 renumber 0