How to make CSS outline cornered?

Question

I have code that provides me that

CSS Code:

  .about-best-big-vector-right {
  width: 1380px;
  float: right;
  border-top: 140px solid #272838;
  border-left: 75px solid transparent;
  position: relative;
  outline: 3px solid #eda225;
  outline-offset: .3rem;
  -moz-outline-radius-bottomleft: 2em;
}

HTML Code: <div class="about-best-big-vector-right"></div>

But I want to achive that and can't make cornered bottom-left?

Answer 1

Don't use border for this, use skew transformation:

.box {
  overflow: hidden;
  width: 40%;
  margin-left: auto;
}

.box::before {
  content: "";
  display: block;
  margin-right: -10px;
  height: 150px;
  background: #000 content-box;
  padding: 5px;
  border: 4px solid orange;
  transform-origin: top;
  transform: skewX(30deg);
}

<div class="box">

</div>