Ordering flex items

Answer 1

Reverse the row order by using row-reverse instead of row for the flex-direction.

flex-direction: row-reverse;

You can also order the children manually by giving them each an order property that takes an integer.

.flex-container :nth-child(1) { order: 3; }
.flex-container :nth-child(2) { order: 2; }
.flex-container :nth-child(3) { order: 1; }

Answer 2

Its easy if you can switch to CSS Grid layout:

• create an grid container on flex-cotainer element

• place the second element to first column (using grid-column: 1) spanning 2 rows (using grid-row: 1 / 3).

See demo below:

.flex-container {
  display: inline-grid;
  grid-template-columns: auto auto;
}

.flex-container div:nth-child(2) {
  grid-column: 1;
  grid-row: 1 / 3;
}

.flex-container > div {
  background-color: DodgerBlue;
  color: white;
  width: 100px;
  margin: 10px;
  text-align: center;
  line-height: 75px;
  font-size: 30px;
}

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

A flexbox solution is hacky at best using negative margins and known heights - see below:

.flex-container {
  display: flex;
  flex-wrap: wrap;
  width: 200px;
}

.flex-container div:nth-child(1) {
  align-self: flex-start;
}

.flex-container div:nth-child(2) {
  order: -1;
  line-height: 170px;
}

.flex-container div:nth-child(3) {
  margin-left: auto;
  margin-top: -85px;
}

.flex-container > div {
  background-color: DodgerBlue;
  color: white;
  width: calc(100px - 20px);
  margin: 10px;
  text-align: center;
  line-height: 75px;
  font-size: 30px;
}

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

Answer 3

You shouldn't use Flexbox for this because it's not designed for it. Consider using CSS Grid instead. Using grid-template-areas, assigning the children where we want them in the layout becomes a trivial task. The DOM order of the grid children becomes irrelevant.

.grid-container {
  display: inline-grid;
  grid-template-areas: "two one"
                       "two three";
}

.grid-container > div {
  background-color: DodgerBlue;
  color: white;
  width: 100px;
  margin: 10px;
  text-align: center;
  line-height: 75px;
  font-size: 30px;
}

.one {
  grid-area: one;
}

.two {
  grid-area: two;
}

.three {
  grid-area: three;
}

<div class="grid-container">
  <div class="one"><a href="#">1</a></div>
  <div class="two"><a href="#">2</a></div>
  <div class="three"><a href="#">3</a></div>
</div>