Exclude featured posts from main WordPress blog loop

excludefeatured.php

/**
 * Exclude featured posts from main blog loop
 */
function bt_exclude_featured_from_blog_index( $query ) {
	if ( ! is_admin() && $query->is_home() && $query->is_main_query() ) {
		$post_ids = bt_featured_post_ids();
		if ( ! empty( $post_ids ) ) {
			$query->set( 'post__not_in', $post_ids );
		}
	}
}
add_action( 'pre_get_posts', 'bt_exclude_featured_from_blog_index' );

/*
* Query featured posts
* Includes the first 4 featured by default. Adjust $num for less or more.
* Uses an ACF True/False field with key "featured_post", which stores a true value as 1.
*/
function bt_featured_post_ids( $num = 4 ) {
	$post_ids = array();

	$args = array(
		'post_type'   => 'post',
		'post_status' => 'publish',
		'showposts'   => $num,
		'orderby'     => 'date',
		'order'       => 'desc',
		'meta_query'  => array(
			array(
				'key'     => 'featured_post',
				'value'   => 1,
				'compare' => '=',
			),
		),
	);

	$c_query = new WP_Query( $args );

	if ( $c_query->have_posts() ) {
		while ( $c_query->have_posts() ) {
			$c_query->the_post();
			$post_ids[] = get_the_ID();
		}
		wp_reset_postdata();

	}

	return $post_ids;
}