Left column and stacked right column using flexbox CSS [duplicate]

Answer 1

First we create a container .Box and set width and height. Honestly, it is just for demo i set 80vw and 80vh. And that container should be a flex element with column orientation flex-flow: column wrap;. And we set the max-width of the largest blocks (.BoxItem--large { max-width: 80%; height: 100%; }) 100% of parents height. It is for wrapping the other elements on the new line/column. So elements from another column should fill all space, so we set .BoxItem--small { max-width: 20%; height: auto; } - yes, 80% + 20% == 100%, that the math. lets change behaviour on the low-width screens. @media screen and (max-width: 600px) { .Box { flex-flow: column nowrap; } } we dont need to wrap elements, so just change that. After that we want every BoxItem element to inherit parents width. .BoxItem { width: 100%; max-width: 100%; } max-width: 100%; for cascading, we dont want care about some old rules like .BoxItem--large { max-width: 80%; } and .BoxItem--small { max-width: 20%; }. And set some order changes.

*,
*:before,
*:after {
  box-sizing: inherit;
}
html {
  box-sizing: border-box;
}
html,
body {
  height: 100%;
  margin: 0;
  padding: 0;
}
body {
  display: -webkit-box;
  display: -webkit-flex;
  display: -ms-flexbox;
  display: flex;
  -webkit-box-align: center;
  -webkit-align-items: center;
      -ms-flex-align: center;
          align-items: center;
  -webkit-box-pack: center;
  -webkit-justify-content: center;
      -ms-flex-pack: center;
          justify-content: center;
  background-color: #F72F4E;
  overflow: hidden;
}


.Box {
  width: 80vw;
  height: 80vh;
  background-color: rgba(0,0,0,.2);
  display: -webkit-box;
  display: -webkit-flex;
  display: -ms-flexbox;
  display: flex;
  -webkit-flex-flow: column wrap;
      -ms-flex-flow: column wrap;
          flex-flow: column wrap;
  -webkit-box-align: baseline;
  -webkit-align-items: baseline;
      -ms-flex-align: baseline;
          align-items: baseline;
}

.BoxItem {
  background-color: #fff;
  border: 1px solid #000;
}
.BoxItem--large {
  max-width: 80%;
  height: 100%;
}
.BoxItem--small {
  max-width: 20%;
  height: auto;
}
@media screen and (max-width: 600px) {
  .Box {
    -webkit-flex-flow: column nowrap;
        -ms-flex-flow: column nowrap;
            flex-flow: column nowrap;
  }
  .BoxItem {
    width: 100%;
    max-width: 100%;
  }
  .BoxItem--large {
    height: auto;
  }
  .BoxItem--1 {
    -webkit-box-ordinal-group: 3;
    -webkit-order: 2;
        -ms-flex-order: 2;
            order: 2;
  }
  .BoxItem--2 {
    -webkit-box-ordinal-group: 2;
    -webkit-order: 1;
        -ms-flex-order: 1;
            order: 1;
  }
  .BoxItem--3 {
    -webkit-box-ordinal-group: 4;
    -webkit-order: 3;
        -ms-flex-order: 3;
            order: 3;
  }
}

<div class="Box">
  <div class="BoxItem BoxItem--large BoxItem--1">Lorem ipsum dolor sit amet, consectetur adipisicing elit. Iusto omnis rerum ea assumenda velit. Dolores ea unde iste esse illo sit, repellat molestias deleniti, voluptas expedita commodi odio possimus amet?</div>
  <div class="BoxItem BoxItem--small BoxItem--2">Lorem ipsum dolor sit amet, consectetur adipisicing elit. Iusto omnis rerum ea assumenda velit.</div>
  <div class="BoxItem BoxItem--small BoxItem--3">Lorem ipsum dolor sit amet, consectetur adipisicing elit. Iusto omnis rerum ea assumenda velit.</div>
</div>

Answer 2

It looks like you were almost there. Just two more steps:

1. Define a height for the flex container

   Without a defined height some browsers may not know where to wrap. Try this:

   .container {
       display: flex;
       flex-direction: column;
       flex-wrap: wrap;
       height: 500px; /* new; value just for demo purposes */
   }
   

2. Turn off wrap on mobile view

   @media (max-width: 500px) {
      .container { flex-wrap: nowrap; } /* new */
      .cell { width: 100%; }
      .cell-1 { order: 2; }
      .cell-2 { order: 1; }
      .cell-3 { order: 3; }
   }
   

.container {
  display: flex;
  flex-direction: column;
  flex-wrap: wrap;
  height: 500px;
}
.cell {
  background: #ccc;
  border: solid 3px black;
  width: 50%;
}
.cell-1 {
  flex-basis: 100%;
}
@media (max-width: 500px) {
  .container {
    flex-wrap: nowrap;
  }
  .cell {
    width: 100%;
  }
  .cell-1 {
    order: 2;
  }
  .cell-2 {
    order: 1;
  }
  .cell-3 {
    order: 3;
  }
}

<h1>Vertical Boxes</h1>
<p>Goal: Have one box on the left, and two boxes on the right that are stacked. All without nesting, so that the order of the boxes can be changed on smaller screen sizes.</p>
<div class="container">
  <div class="cell cell-1">
    <h2>One</h2>
    Lorem ipsum dolor sit amet, consectetur adipisicing elit. Iusto pariatur rerum, illum accusantium cupiditate ipsam, eaque quae fugit cum assumenda ad. Modi, excepturi. Assumenda, nobis, consequatur? Aliquid repellendus quis, iure. Lorem ipsum dolor sit
    amet, consectetur adipisicing elit. Iusto pariatur rerum, illum accusantium cupiditate ipsam, eaque quae fugit cum assumenda ad. Modi, excepturi. Assumenda, nobis, consequatur? Aliquid repellendus quis, iure. Lorem ipsum dolor sit amet, consectetur
    adipisicing elit. Iusto pariatur rerum, illum accusantium cupiditate ipsam, eaque quae fugit cum assumenda ad. Modi, excepturi. Assumenda, nobis, consequatur? Aliquid repellendus quis, iure. Lorem ipsum dolor sit amet, consectetur adipisicing elit.
    Iusto pariatur rerum, illum accusantium cupiditate ipsam, eaque quae fugit cum assumenda ad. Modi, excepturi. Assumenda, nobis, consequatur? Aliquid repellendus quis, iure.
  </div>
  <div class="cell cell-2">
    <h2>Two</h2>
    Lorem ipsum dolor sit amet, consectetur adipisicing elit. Iste mollitia temporibus id sint illum doloremque pariatur nulla vel soluta, nostrum vitae, suscipit ea natus sed eaque in velit deserunt deleniti!
  </div>
  <div class="cell cell-3">
    <h2>Three</h2>
    Lorem ipsum dolor sit amet, consectetur adipisicing elit. Impedit, architecto perferendis voluptatum accusantium est ipsam fugit, laudantium fugiat nostrum consectetur earum. Asperiores, similique deleniti nobis nemo error, iste iure architecto.
  </div>
</div>

revised codepen