FlexSlider slider gallery HTML elements

add_action( 'wp_enqueue_scripts', function() {

	wp_enqueue_style(
		'flexslider',
		'//cdnjs.cloudflare.com/ajax/libs/flexslider/2.7.2/flexslider.min.css'
	);

	wp_enqueue_script( 'jquery' );

	wp_enqueue_script(
		'flexslider',
		'//cdnjs.cloudflare.com/ajax/libs/flexslider/2.7.2/jquery.flexslider-min.js',
		[ 'jquery' ]
	);

	wp_add_inline_script( 'jquery', '

		jQuery( document ).ready( function( $ ) {

			var slider1 = $( ".flexslider" );

			slider1.flexslider( {
				animation: "slide",
				animationLoop: false,
				itemWidth: 300,
				itemMargin: 36,
				minItems: 1,
				maxItems: 3
			} );

			$( window ).resize( function() {
				slider1.resize();
			} );

		} );

	', 'after' );

} );

I also recommend placing a CSS rule inside WP Admin > Appearance > Customizer > CSS to hide all but the first slide during page load:

.flexslider .wp-block-cover:not( :first-child ) {
	display: none;
}