<div class="container">
  <div class="item item01">01</div>
  <div class="item item02">02</div>
  <div class="item item03">03</div>
  <div class="item item04">04</div>
  <div class="item item05">05</div>
  <div class="item item06">06</div>
  <div class="item item07">07</div>
  <div class="item item08">08</div>
  <div class="item item09">09</div>
  <div class="item item10">10</div>
</div>

*,
*::before,
*::after {
  box-sizing: border-box;
}

body {
  font-family: system-ui, sans-serif;
}

.container {
  display: flex;
  flex-flow: row wrap;
  gap: 2rem 1rem;
}

.item {
  height: 200px;
  width: 400px;
  background: lightgrey;

  display: flex;
  place-content: center;
  align-items: center;

  font-size: 2rem;
}