function my_admin_menu() {
		add_menu_page(
			__( 'Sample page', 'my-textdomain' ),
			__( 'Sample menu', 'my-textdomain' ),
			'manage_options',
			'sample-page',
			'my_admin_page_contents',
			'dashicons-schedule',
			3
		);
	}

	add_action( 'admin_menu', 'my_admin_menu' );


	function my_admin_page_contents() {
		?>
			<h1>
				<?php esc_html_e( 'Welcome to my custom admin page.', 'my-plugin-textdomain' ); ?>
			</h1>
		<?php
	}