Flex Example

HTML

<div class="container">
    <div>
      <div class='h100'>Div 2</div>
      <div class='h100'>Div 3</div>
    </div>
    <div>
    <div class='h100percent'>
    <div>Div 4</div>
    </div>
</div>

CSS

.h100 {
  height: 50px;
  display: flex;
	flex-direction: column;
	flex-wrap: wrap-reverse;
	justify-content: center;
	align-items: stretch;
	align-content: flex-start;
}
.h100percent {
    height: 100%;
  display: flex;
	flex-direction: column;
	flex-wrap: wrap-reverse;
	justify-content: center;
	align-items: stretch;
	align-content: flex-start;
}
.container {
      border: 1px solid black;
    background: #ececec;
    padding: 10px;
    margin-left: 10px;
    flex: 1;
    height: 300px;
	display: flex;
	flex-direction: column;
	flex-wrap: wrap-reverse;
	justify-content: flex-start;
	align-items: stretch;
	align-content: flex-start;
}