html - Flexbox center and bottom right item

Question

I'm trying to achieve the following result using flexbox:

I tried the with the following html but I can't get it to work.

<div class=" flex-center">
    <div class="flex-item-center">
        <p>
            Some text in box A
        </p>
    </div>
    <div class="flex-item-bottom">
        <p>Some text in box B....</p>
    </div>
</div>

CSS:

.flex-center {
  display: flex;
  align-items: center;
  align-content: center;
  justify-content: center;
}
.flex-item-center {
  align-self: center;
}

.flex-item-bottom {
  align-self: flex-end;
}

How can I make it look like the image?

Answer 1

I've made a posible solution.

.flex-center {
  background-color: #739FD0;
  color: #000000;
  display: flex;
  flex-direction: row;
  flex-wrap: wrap;
  justify-content: center;
  align-content: center;
  align-items: center;
  height: 400px;
}
.flex-center-bottom {
  background-color: #739FD0;
  color: #000000;
  display: flex;
  flex-direction: row;
  flex-wrap: wrap;
  justify-content: flex-end;
  align-content: center;
  align-items: center;
}
.flex-item-center {
  border: solid 2px #4675AA;
  order: 0;
  flex: 0 1 auto;
  align-self: center;
}
.flex-item-bottom {
  border: solid 2px #4675AA;
  order: 1;
  flex: 0 1 auto;
  align-self: flex-end;
}

<div class="flex-center">
  <div class="flex-item-center">
    <p>DROP FILES HERE</p>
  </div>
</div>
<div class="flex-center-bottom">
  <div class="flex-item-center">
    <p>Hint: You can also drop files in the all files page</p>
  </div>
</div>