A header template. Import {latte} block in '@layout.default.latte' using macro {import '../path-to-latte-template'} and declare this block as {include pageHeader}. Between macros {import} and {include} redefine template of used blocks like this:

{define #searchIcon}
	<i class="o-header3__icon a-icon-search" aria-hidden="true"></i>
{/define}

Take a look at source of {latte} template to discover available hooks to customization.

Include template of menu from 'm-nav-header' package to 'menuControl.latte':

{import "${nodeModulesPath}/aitomic-m-nav-header/src/control/m-nav-header.latte"}

{include #m-nav-header, submenu => 'm-nav-mega', state => 'inline', menuClass => 'o-header3__menu'}

The variable 'submenu' has options 'm-nav-dropdown' and 'm-nav-mega' representing style of the submenu.

Import and include {block #m-search-form} into '@layout.default.latte' at the end of {block #aiLayout} and define search translation:

{define #searchTranslation}
	{_"Search"}
	{_"Type & hit enter..."}
{/define}