<div class="grid">
  <div class="item item1">1</div>
  <div class="item item2">2</div>
  <div class="item item3">3</div>
  <div class="item item4">4</div>
</div>

.grid {
  display: grid;
  grid-gap: 20px;

  grid: 100px 300px / auto-flow 200px;
  /* shorthand for: */ 
  /*
   grid-template-rows: 100px 300px;
   grid-auto-flow: column;
   grid-auto-columns: 200px;
  */
}