<div class="grid">
  <div class="col">
    <div class="box"></div>
  </div>
  <div class="col">
     <div class="box"></div>
  </div>
  <div class="col">
     <div class="box"></div>
  </div>
</div>

.grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  background: url(https://picsum.photos/1000) center / cover no-repeat;
}
.col {
  padding: 5px;
  overflow: hidden;
}
.box {
  border-radius: 20px;
  height: 200px;
  box-shadow: 0 0 0 20px lime;
}