Edit in JSFiddle

<div class="flex-container">
  <div>1</div>
  <div>2</div>
  <div>3</div>
</div>

<div class="flex-container flex-start">
  <div>1</div>
  <div>2</div>
  <div>3</div>
</div>

<div class="flex-container flex-end">
  <div>1</div>
  <div>2</div>
  <div>3</div>
</div>

<div class="flex-container space-around">
  <div>1</div>
  <div>2</div>
  <div>3</div>
</div>
.flex-container {
  display: flex;
  flex-flow: row;
  background: #ddd;
  justify-content: center;
}
.flex-start{
  background:#cccccc;
  justify-content:flex-start;
}

.flex-end{
  background:#ddd;
  justify-content:flex-end;
}

.space-around{
  background:#ccc;
  justify-content:space-around;
}

.flex-container>div {
  background-color: #ffffff;
  width: 100px;
  margin: 10px;
  text-align: center;
  line-height: 75px;
  font-size: 30px;
  border: 2px solid #00a9d4;
  font-family: Calibri, sans-serif;
  border-radius: .25rem;
}