functions.php

add_action('wpmu_new_blog', 'wpb_create_my_pages', 10, 2);

function wpb_create_my_pages($blog_id, $user_id){
  switch_to_blog($blog_id);

  // create new page
  $page_id = wp_insert_post(array(
    'post_title'     => 'Home',
    'post_name'      => 'home',
    'post_content'   => 'Welcome to our shop.',
    'post_status'    => 'publish',
    'post_author'    => $user_id, // or "1" (super-admin?)
    'post_type'      => 'page',
    'menu_order'     => 1,
    'comment_status' => 'closed',
    'ping_status'    => 'closed',
 ));

  update_option( 'page_on_front', $page_id );
  update_option( 'show_on_front', 'page' );

  // Find and delete the WP default 'Sample Page'
  $defaultPage = get_page_by_title( 'Sample Page' );
  wp_delete_post( $defaultPage->ID );

  wp_insert_post(array(
    'post_title'     => 'About Us',
    'post_name'      => 'about-us',
    'post_content'   => 'Add information about your group here.',
    'post_status'    => 'publish',
    'post_author'    => $user_id, // or "1" (super-admin?)
    'post_type'      => 'page',
    'menu_order'     => 1,
    'comment_status' => 'closed',
    'ping_status'    => 'closed',
 ));

  wp_insert_post(array(
    'post_title'     => 'Contact Us',
    'post_name'      => 'contact-us',
    'post_content'   => 'Add information about contacting you here.',
    'post_status'    => 'publish',
    'post_author'    => $user_id, // or "1" (super-admin?)
    'post_type'      => 'page',
    'menu_order'     => 1,
    'comment_status' => 'closed',
    'ping_status'    => 'closed',
 ));
  restore_current_blog();
}