<div class="grid">
<div class="item"></div>
<div class="item"></div>
<div class="item"></div>
<div class="item"></div>
<div class="item"></div>
<div class="item"></div>
...
</div>
.grid {
display: grid;
grid-template-columns: 1fr 1fr;
}
.item:nth-child(3n + 3) {
grid-column: span 2;
}