* {box-sizing: border-box;}

HTML

<!-- Learn about this code on MDN: https://developer.mozilla.org/en-US/docs/Glossary/Grid_Lines -->

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

CSS

* {box-sizing: border-box;}

.wrapper {
    border: 2px solid #f76707;
    border-radius: 5px;
    background-color: #fff4e6;
     display: grid;
     grid-template-columns: repeat(3, 1fr);
     grid-template-rows: repeat(3, 100px);
}

.wrapper > div {
    border: 2px solid #ffa94d;
    border-radius: 5px;
    background-color: #ffd8a8;
    padding: 1em;
    color: #d9480f;
}
.wrapper {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: 100px 100px;
}
.item {
  grid-column:1/span 3;
}