I'm basically trying to get the baseline of the value to align with the baseline of the bottom unit instead of the first as it's happening in my code below.
I can get it to work if I ditch flexbox altogether but I need it for responsiveness.
The canonical advice seems to be to wrap flex items in inline-block but, as you can see from that codepen, it doesn't seem to work for me.
Here's the codepen where I've been trying stuff: https://codepen.io/jskrt/pen/OJyXxyv
.value_and_unit {
  display: flex;
  flex-flow: row nowrap;
  justify-content: flex-start;
  align-items: baseline;
}
.value {
  line-height: 1;
  font-size: 120px;
  margin-right: 10px;
}
.unit_container {
  display: flex;
  flex-flow: column nowrap;
  justify-content: flex-end;
  align-items: center;
}
.divider {
  width: 100%;
}
.inline-block {
  display: inline-block;
}
<div class="value_and_unit">
  <span class="value">
    340
  </span>
  <div class="unit_container">
    <span class="unit">
      m
    </span>
    <hr class="divider" />
    <span class="unit">
      s
    </span>
  </div>
</div>