<div class="flex-container">
  <div class="second">
    <p>A</p>
    <p>order not specified</p>
  </div>
  <div class="third">
    <p>B</p>
    <p>order: 1;</p>
  </div>
  <div class="first">
    <p>C</p>
    <p>order: -1;</p>
  </div>
</div>

.flex-container {
  display: flex;
  background-color: lighten(darkorange, 20%);
  border: 1px solid black;
  
  & div {
    border: 1px solid black;
    width: 100px;
    height: 100px;
    background-color: darkorange;
    margin: 10px;
  }
  
  .first {
    order: -1;
  }
  
  .second {
  }
  
  .third {
    order: 1;
  }
  
  p {
    text-align: center;
  }
}