Not able to align items with justify-content

Question

In a flex container, not able to align the items towards the flex-axis (when the flex-direction is column).

Please refer the code snippet below.

I would expect the result with the items aligned from the bottom (justify-content: flex-end supposed to be in effect) . But the items are displayed as if justify-content: flex-start is in effect.

Any idea where I am erring?

Taking hint from @Temani Afif's comment I could fix it.

I have to make sure the container height is 100%. Also height of the html and body elements are also 100%.

html, body{
            height: 100%;
 }

html, body {
     height: 100%;
}
.flex-container {
  padding: 0;
  margin: 0;
  list-style: none;
  display: flex;
  flex-direction: column;
  height: 100%;
}

.flex-start { 
  justify-content: flex-start; 
}

.flex-end { 
  justify-content: flex-end; 
}  
.flex-end li {
  background: gold;
}

.center { 
  justify-content: center; 
}  
.center li {
  background: deepskyblue;
}

.space-between { 
  justify-content: space-between; 
}  
.space-between li {
  background: lightgreen;
}

.space-around { 
  justify-content: space-around; 
}
.space-around li {
  background: hotpink; 
}

.space-evenly { 
  justify-content: space-evenly; 
}
.space-evenly li {
  background: #bada55; 
}

.flex-item {
  background: tomato;
  padding: 5px;
  width: 35px;
  height: 25px;
  margin: 5px;
  line-height: 25px;
  color: white;
  font-weight: bold;
  font-size: 2em;
  text-align: center;
}

<ul class="flex-container flex-end">
  <li class="flex-item">1</li>
  <li class="flex-item">2</li>
  <li class="flex-item">3</li>

</ul>