Add custom images sizes to your wordpress theme. See https://since1979.dev/snippet-001-adding-custom-images-sizes/

snippet-001-register-images-sizes.php

<?php
/**
 * register_thumbnail_sizes.
 *
 * Register custom images sizes with WordPress,
 * These images will be created when an image is uploaded,
 * and then stored in the /wp-content/uploads directory.
 *
 * @see  https://since1979.dev/snippet-001-adding-custom-images-sizes/
 *
 * @uses add_theme_support https://developer.wordpress.org/reference/functions/add_theme_support/
 * @uses add_image_size https://developer.wordpress.org/reference/functions/add_image_size/
 */
function register_thumbnail_sizes()
{
    // Show the 'featured image' option in the editor.
    add_theme_support('post-thumbnails');

    // register the actual custom image sizes.
    add_image_size('full-page-width', 1000, 9999, true);
    add_image_size('half-page-width', 500, 9999, true);
    add_image_size('square', 500, 500, true);
}

/**
 * Hook: after_setup_theme.
 *
 * @uses add_action() https://developer.wordpress.org/reference/functions/add_action/
 * @uses init https://developer.wordpress.org/reference/hooks/init/
 */
add_action('init', 'register_thumbnail_sizes', 1);