[CSS] Cut corners with border

cut-corners-with-border.css

.wrap {
  display: inline-block;
  padding: 20px;
  background-color: SeaGreen;
}

.elem {
  width: 300px;
  position: relative;
  border-radius: 10px;
  background-image: linear-gradient(135deg, transparent 5%, #333 5% 95%, transparent 95%);
  padding: 20px;
  z-index: 0;
}

.elem::before {
  z-index: -1;
  content: '';
  position: absolute;
  left: 3px;
  right: 3px;
  top: 3px;
  bottom: 3px;
  border-radius: 7px;
  background-image: linear-gradient(135deg, transparent 5%, orange 5% 95%, transparent 95%);
}

screenshot.jpg