“Each State shall appoint, in such Manner as the Legislature thereof may direct, a Number of Electors, equal to the whole Number of Senators and Representatives to which the State may be entitled in the Congress: but no Senator or Representative, or Person holding an Office of Trust or Profit under the United States, shall be appointed an Elector.“
Technically, a vote of the people isn’t even constitutionally required for the appointment of EC electors.
How they are appointed is completely left up to each individual state legislature,