SOURCE

<div class="container">
  <div class="item">1</div>
  <div class="item">2</div>
  <div class="item">3</div>
  <div class="item">4</div>
  <div class="item">5</div>
  <div class="item">6</div>
</div>

.container {
  display: grid;
  width: 400px;
  border: 1px solid blue;
  grid-template-rows: 100px 100px 100px;
  grid-template-columns: 80px auto;
}

.item {
  background: #ddd;
  margin: 10px;
}