Basic Nav Menu Walker Structure for custom WordPress themes.

barebones-walker.php

<?php
class myWalker extends Walker_Nav_Menu {
	// Displays start of a level. E.g '<ul>'
	// @see Walker::start_lvl()
	function start_lvl(&$output, $depth=0, $args=[]) {
		$output .= '<ul>';
	}
	// Displays end of a level. E.g '</ul>'
	// @see Walker::end_lvl()
	function end_lvl(&$output, $depth=0, $args=[]) {
		$output .= '</ul>';
	}
	// Displays start of an element. E.g '<li> Item Name'
	// @see Walker::start_el()
	function start_el(&$output, $item, $depth=0, $args=[]) {
		$output.= '<li>'.esc_attr($item->title);
	}
	// Displays end of an element. E.g '</li>'
	// @see Walker::end_el()
	function end_el(&$output, $item, $depth=0, $args=[]) {
		$output .= '</li>';
	}
}
?>