<!DOCTYPE html>
<style>
.multicol {
    width: 60px;
    -webkit-column-width: 20px;
    -webkit-column-gap: 0;
    column-fill: auto;
    height: 60px;
}
.square {
    width: 20px;
    height: 20px;
    background: green;
}
.layer { will-change: transform; }
</style>

<p>There should a green square below.</p>
<div class="multicol">
    <div class="square"></div>
    <div class="square"></div>
    <div class="layer"> <!-- bottom of first column -->
        <div class="square"></div>
    </div>
    <div class="square"></div>
    <div class="layer"> <!-- middle of second column -->
        <div class="square"></div>
    </div>
    <div class="square"></div>
    <div class="layer"> <!-- entire third column -->
        <div class="square"></div>
        <div class="square"></div>
        <div class="square"></div>
    </div>
</div>