using a flex item as a flex container

Question

I wanted to use flexbox with a column layout, but I wanted the top n - 1 flex items to be pinned to the top and the nth flex item to be pinned to the bottom of the main flex container area.

I solved this by using the nth flex item to also be a new flexbox/flex container using justify-content: flex-end, but I couldn't find any examples that were doing this - so is this a correct/acceptable solution according to the standard and, if not, how would I otherwise go about this with flexbox?

Here's a quick example:

.flex-container {
  display: -webkit-flex;
  display: flex;
  -webkit-flex-direction: column;
  flex-direction: column;
  width: 300px;
  height: 240px;
  background-color: Silver;
}
.flex-container-bottom {
  display: -webkit-flex;
  display: flex;
  -webkit-flex-direction: column;
  flex-direction: column;
  width: 300px;
  height: 240px;
  background-color: orange;
  -webkit-justify-content: flex-end;
  -ms-flex-pack: end;
  justify-content: flex-end;
}
.flex-item {
  background-color: DeepSkyBlue;
  width: 100px;
  height: 100px;
  margin: 5px;
}
.flex-item-bottom {
  background-color: red;
  width: 100%;
  height: 50px;
}

<div class="flex-container">
  <div class="flex-item">flex item 1</div>
  <div class="flex-item flex-container-bottom">
    <div class="flex-item-bottom">flex item 2</div>
  </div>
</div>

Answer 1

The spec isn't very clear on this, but it states that "Each in-flow child of a flex container becomes a flex item, and each contiguous run of text that is directly contained inside a flex container is wrapped in an anonymous flex item." This seems to imply that if I put a flex container inside another flex container that the inner flex container would also implicitly become a flex item for its containing flex container even if this is not explicitly defined. Example 1 of the specification shows a flex container within a flex container and assuming it is legal syntax it follows that my use case may also be legal, but the section with example 1 is marked as non-normative... (╯°□°）╯︵ ┻━┻... At this point I'm just going to assume this is correct.