Setting layout with flexbox - css

Question

I have a wireframe below and want to see what's the best way to code this with flexbox.
I have coded a simple flexbox grid system but my wireframe requires more customization than what I have on my grid system.
I have parent div has display: flex and have 2 child divs have flex:1 and flex: 0 0 40%.
What is the best way to add content div(gray boxes inside on blue and red) that will stay with rest of main wrapper(entire gray box sets to max-width: 1400px)?
Thank you.

Answer 1

Here's the general idea.
Positioned pseudo-elements, one for each section of the row. With a suitable width (note that the body should have overflow-x:hidden) and appropriate positioning values.
* {
box-sizing: border-box;
}
body {
overflow-x: hidden;
}
.wrapper {
min-height: 100vh; /* for demo purposes */
width: 60%;
margin: auto;
background: grey;
display: flex;
flex-direction: column;
}
header {
height: 20vh;
background: green;
}
.inner {
height: 30vh;
display: flex;
}
main {
background: blue;
flex: 1;
border: 2px solid black;
}
aside {
background: red;
flex: 0 0 40%;
border: 2px solid black;
}
.other {
background: pink;
flex: 1;
}
/* magic section */
.extend {
position: relative;
}
.extend::after {
content: '';
position: absolute;
width: 100vw;
top: 0;
height: 100%;
background: inherit;
z-index: -1;
}
.left::after {
right: 0;
}
.right::after {
left: 0;
}
<div class="wrapper">
<header></header>
<div class="inner">
<main class="extend left"></main>
<aside class="extend right"></aside>
</div>
<div class="other"></div>
</div>