Wordpress PHP grid layout presentation - php

Question

I want to change the layout of a grid of videos on a site. It's Wordpress.
Currently the PHP displays the grid in a 3/2 layout over two rows and then duplicates it depending on how many videos you choose to display.
I understand the code enough to know that we are setting 5, and splitting into 3/2. And i can set it to 6 and split into 3/3 or 4/2.....and so on
But I need to change the layout so we have a row of 3, then 3 but with the first two of the second row stacked on top of each other 1/3rd width and the third 2/3rd width. like below.
new layout to be acheived
Current PHP that does the layout: ( I understand that CSS might have to be changed but I can do that)
<article class="col-1-<?php if(($i%5==0)||(($i+1)%5==0)){ echo "2"; } else { echo "3"; } ?>" id="post-<?php echo $page->ID; ?>">
Full block:
<article class="col-1-<?php if(($i%5==0)||(($i+1)%5==0)){ echo "2"; } else { echo "3"; } ?>" id="post-<?php echo $page->ID; ?>">
<a href="<?php echo get_page_link($page->ID); ?>">
<?php if ( $detect->isMobile() ) {
if (has_post_thumbnail( $page->ID ) ){ ?>
<img src="<?php echo $image[0]; ?>" alt="<?php echo $title; ?>" width="160" height="90">
<?php } ?>
<?php } else { ?>
<?php if(get_field('looping_thumb_preview', $page->ID)){ ?>
<video playinline preload="auto" loop="yes">
<source src="<?php echo get_field('looping_thumb_preview', $page->ID); ?>" type="video/mp4">
Your browser does not support the video tag.
</video>
<?php } else if(get_field('looping_thumb', $page->ID)){ ?>
<video playinline preload="auto" loop="yes">
<source src="<?php echo get_field('looping_thumb', $page->ID); ?>" type="video/mp4">Your browser does not support the video tag.</video>
<?php } else if (has_post_thumbnail( $page->ID ) ){ ?>
<img src="<?php echo $image[0]; ?>" alt="<?php echo $title; ?>">
<?php } else { ?>
<img src="<?php bloginfo( 'template_url' ); ?>/images/blank.png" alt="<?php echo $title; ?>">
<?php } ?>
<?php } ?>
<div class="center-content">
<h1<?php if(get_field('subtitle', $page->ID)){ echo ' class="hassubtitle"';} else { echo ' class="nosubtitle"'; }?>><?php echo $title;?></h1>
<div class="underline"></div>
<?php if(get_field('subtitle', $page->ID)) { echo "<h2>" . get_field('subtitle', $page->ID) . "</h2>"; }
?>
</div>
</a>
</article>
Thanks in advance for any help