I've checked out https://gridbyexample.com/example and have been trying myself to make this work, but can't get it to fit right. Check out the attached image for what I'm trying to do. Is there an easy CSS-Grid way to do this? 
What I have so far for CSS:
.main-container {
display: grid;
grid-gap: 15px;
grid-template-columns: repeat(auto-fit, minmax(225px, 1fr));
}
.box {
height: min-content;
}
/* Targeting the 2nd content block in column 3 */
.box.d {
grid-column: 3/6;
}
What I have so far for HTML:
<div class="main-container">
<div class=-"box a">Content Here</div>
<div class=-"box b">Content Here</div>
<div class=-"box c">Content Here</div>
<div class=-"box d">Content Here</div>
<div class=-"box e">Content Here</div>
<div class=-"box f">Content Here</div>
<div>