Is there a simple way to make a custom border shape for an HTML <div>?

Question

I am building a webpage with cards arranged in a grid.

However, I would like my cards to have a unique shape, rather than just being rectangles. The shape I would like them to be is the shape of a manilla folder (pictured below)

Is there any relatively simply way to make a div with this shape?

Answer 1

Here is a start using only html and css:

body {
  padding: 50px;
}

div {
  position: relative;
  z-index: 1;
  white-space: nowrap;
}

div .slant {
  position: relative;
  display: inline-block;
  color: inherit;
  text-decoration: none;
  margin: 0 -14px -4px;
  width: 40px;
}

div .slant::before,
main {
  border: 0.2em solid #000;
  background: #000;
}

div .slant::before {
  content: "";
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0.5em;
  left: 0;
  z-index: -1;
  border-bottom: none;
  border-radius: 5px 5px 0 0;
  background: #000;
  transform: perspective(5px) rotateX(2deg);
  transform-origin: bottom;
}

div.left .slant {
  padding: 1.5em 2em 1em 1em;
}

div.left .slant::before {
  transform-origin: bottom left;
}

main {
  display: block;
  margin: -8px 0 30px -14px;
  padding: 1em;
  border-radius: 0 5px 5px 5px;
  width: 200px;
  height: 300px;
}

<div class="left">
  <div class="slant"></div>
</div>
<main>
</main>