<div class="rowflex">
  <div class="gauche">gauche</div>
  <div class="milieu">milieu</div>
  <div class="droite">droite</div>
</div>

.rowflex{
  width : 300px;
  height: 150px;
  align-items: flex-start;
  border : thin solid silver;	
  display : flex;
}
.rowflex div{
  padding: 5px;
  width: 100px;
}
.rowflex .milieu{
  background-color: orange;
  align-self: flex-end;
}
.rowflex .gauche{
  background-color: pink;
}
.rowflex .droite{
  background-color: silver;
}