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

.container {
  display: grid;
  height: 90vh;
  width: 90vw;
  grid-template-rows: repeat(3, 1fr);
  border: 3px solid black;
  margin: auto;
}

.container::before, .container::after {
  content: "";
}

.item {
  background: teal;
  width: 60vw;
  margin: 0 auto;
}