<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 class="item"></div>
  <div class="item"></div>
  <div class="item"></div>
  <div class="item"></div>
  <div class="item"></div>
</div>

body {
  padding: 1rem;
}
.item {
  height: 50px;
  background: green;
}

.grid {
  display: grid;
  grid-gap: 1rem;
  grid-template-columns: 1fr 1fr;
}
.item:nth-child(3n + 3) {
  background: red;
  grid-column: span 2;
}