With the following markup, I want to have the below-attached layout using the flex system (not with grid) and without changing the markup structure.
HTML:
<div class="container">
<div class="box box-1">item1</div>
<div class="box box-2">item2</div>
<div class="box box-3">item3</div>
<div class="box box-4">item4</div>
<div class="box box-5">item5</div>
<div class="box box-6">item6</div>
</div>