How to create a custom template with plugin?

I had coded a custom template and uploaded it to my theme’s directory. I would like to give the users ability to use that template without having to upload the file to their theme directory. I googled and found something that supposedly, did what I was looking for.

add_filter( 'page_template', 'wpa3396_page_template' );
function wpa3396_page_template( $page_template )
{
    if ( is_page( 'my-custom-page-slug' ) ) {
        $page_template = dirname( __FILE__ ) . '/custom-page-template.php';
    }
    return $page_template;
}

Basically, I would include the custom-page-template.php with in my plugins folder. Then whenever a particular page is opened (i.e. mysite.com/my-custom-page-slug), the page would use the custom-page-template.php as its template. How can I make the above code work? I just want to include the custom template in my plugin folder and make a particular page use that template. Please help.