How to split chunks?

Hello! For a site with lots of articles I want to display the latest 15 articles, interspersed with other content, on the homepage. I’m looking to create a structure like this:

[Chunk of 3 articles]
[Chunk of 3 articles]
[Chunk of 3 articles]
[Chunk of 3 articles]
[Chunk of 3 articles]

But am not sure how to go about saving/splitting up the chunked collection so that I might insert content between chunks:

// Adapted from another post on the forum

<?php $projects = $articles;
      $chunks   = $projects->limit(15)->chunk(3); ?>

    <section class="articles-recent">
      <?php foreach($chunks as $items): ?>
          <?php foreach($items as $project): ?>
            <a href="<?= $project->url() ?>">
              <imgsrc="<?= $project->coverimage()->toFile()->url() ?>" alt="" />
          <?php endforeach; ?>
      <?php endforeach ?>

So having each chunk as something I can loop through independently.
Is this possible? Is chunk() the right way to approach this?

Thank you!

You can get an individual chunk with the first(), last() or nth() methods.

Or use a counter variable and then check the value of that counter. Eg. if counter equals 1, insert banner x.

Simple! Thank you. And some more characters.