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

body {
  padding: 50px;
  font: 1em Helvetica Neue, Helvetica, Arial, sans-serif;
}

.grid {
  border: 5px solid rgb(111,41,97);
  display: grid;
  grid-template-columns: [full-start] 1fr [main-start] 2fr 2fr [main-end full-end];
  grid-template-rows: repeat(5, 50px);
  inline-size: 500px;
}

.item {
  grid-column: main-start / main-end;
  grid-row: 1 / 4;
}

.grid > * {
  background-color: rgba(111,41,97,.4);
  border-radius: 5px;
  padding: 10px;
}