Edit in JSFiddle

<ul class="flex-container row">
  <li class="flex-item">1</li>
  <li class="flex-item">2</li>
  <li class="flex-item">3</li>
  <li class="flex-item">4</li>
  <li class="flex-item">5</li>
</ul>
<ul class="flex-container row-reverse">
  <li class="flex-item">1</li>
  <li class="flex-item">2</li>
  <li class="flex-item">3</li>
  <li class="flex-item">4</li>
  <li class="flex-item">5</li>
</ul>

<ul class="flex-container column">
  <li class="flex-item">1</li>
  <li class="flex-item">2</li>
  <li class="flex-item">3</li>
  <li class="flex-item">4</li>
  <li class="flex-item">5</li>
</ul>
<ul class="flex-container column-reverse">
  <li class="flex-item">1</li>
  <li class="flex-item">2</li>
  <li class="flex-item">3</li>
  <li class="flex-item">4</li>
  <li class="flex-item">5</li>
</ul>

.flex-container {
  padding: 0;
  margin: 0;
  list-style: none;
  
  -ms-box-orient: horizontal;
  display: -webkit-box;
  display: -moz-box;
  display: -ms-flexbox;
  display: -moz-flex;
  display: -webkit-flex;
  display: flex;
}

.row            { 
  -webkit-flex-direction: row; 
  flex-direction: row;
}

.row-reverse    { 
  -webkit-flex-direction: row-reverse; 
  flex-direction: row-reverse;
}  
.row-reverse li {
  background: gold;
}

.column { 
  -webkit-flex-direction: column; 
  flex-direction: column;
  float: left;
}
.column li {
  background: deepskyblue;
}

.column-reverse { 
  -webkit-flex-direction: column-reverse; 
  flex-direction: column-reverse;
  float: right;
}
.column-reverse li {
  background: lightgreen;
}

.flex-item {
  background: tomato;
  padding: 5px;
  width: 50px;
  height: 50px;
  margin: 5px;
  
  line-height: 50px;
  color: white;
  font-weight: bold;
  font-size: 2em;
  text-align: center;
}