HTML

html div grid 9x9

.grid {
  display: flex;
  flex-wrap: wrap;
  align-items: flex-end;
}

.cell {
  flex: 0 0 33%;
  height: 100px;
  width: 100px;
  margin-bottom: 5px;
}

html div grid 9x9

<div class="grid">
  <div class="cell" style="background-color: green">1</div>
  <div class="cell" style="background-color: red">1</div>
  <div class="cell" style="background-color: blue">1</div>
  <div class="cell" style="background-color: yellow">1</div>
</div>