Gist for my "WordPress: Managing Your Theme's Footer With Widgets." tutorial/article on https://since1979.dev/wordpress-adding-widget-areas-to-your-themes-footer/

register-widgets-all.php

function register_widget_areas() {

  register_sidebar( array(
    'name'          => 'Footer area one',
    'id'            => 'footer_area_one',
    'description'   => 'This widget area discription',
    'before_widget' => '<section class="footer-area footer-area-one">',
    'after_widget'  => '</section>',
    'before_title'  => '<h4>',
    'after_title'   => '</h4>',
  ));

  register_sidebar( array(
    'name'          => 'Footer area two',
    'id'            => 'footer_area_two',
    'description'   => 'This widget area discription',
    'before_widget' => '<section class="footer-area footer-area-two">',
    'after_widget'  => '</section>',
    'before_title'  => '<h4>',
    'after_title'   => '</h4>',
  ));

  register_sidebar( array(
    'name'          => 'Footer area three',
    'id'            => 'footer_area_three',
    'description'   => 'This widget area discription',
    'before_widget' => '<section class="footer-area footer-area-three">',
    'after_widget'  => '</section>',
    'before_title'  => '<h4>',
    'after_title'   => '</h4>',
  ));

  register_sidebar( array(
    'name'          => 'Footer area four',
    'id'            => 'footer_area_four',
    'description'   => 'This widget area discription',
    'before_widget' => '<section class="footer-area footer-area-three">',
    'after_widget'  => '</section>',
    'before_title'  => '<h4>',
    'after_title'   => '</h4>',
  ));

}

add_action( 'widgets_init', 'register_widget_areas' );