[解決済み] フレックスコンテナ内の等高線列

.list {
  display: flex;
  flex-wrap: wrap;
  max-width: 500px;
}
.list-item {
  background-color: #ccc;
  display: flex;
  padding: 0.5em;
  width: 25%;
  margin-right: 1%;
  margin-bottom: 20px;
}
.list-content {
  width: 100%;
}

<ul class="list">
  <li class="list-item">
    <div class="list-content">
      <h2>box 1</h2>
      <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit.</p>
    </div>
  </li>
  <li class="list-item">
    <div class="list-content">
      <h3>box 2</h3>
      <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit.</p>
    </div>
  </li>

  <li class="list-item">
    <div class="list-content">
      <h3>box 2</h3>
      <p>Lorem ipsum dolor</p>
    </div>
  </li>

  <li class="list-item">
    <div class="list-content">
      <h3>box 2</h3>
      <p>Lorem ipsum dolor</p>
    </div>
  </li>
  <li class="list-item">
    <div class="list-content">
      <h1>h1</h1>
    </div>
  </li>
</ul>