JSFiddle - React, Tailwind, and code Playground

HTML

<div class="hexagon"></div>
<div class="hexagon image"></div>
<div class="hexagon double"></div>

CSS

.hexagon {
  position: relative;
  height: 150px;
  width: 150px;
  background: black;
}
.hexagon:before, .double:after {
  position: absolute;
  content: '';
}
.hexagon:before {
  top: 4px;  /* border width */
  left: 4px;  /* border width */
  height: calc(100% - 8px);  /* 100% - (2 * border width) */
  width: calc(100% - 8px);  /* 100% - (2 * border width) */
  background: #6c6;
}
.hexagon, .hexagon:before, .double:after {
  -webkit-clip-path: polygon(50% 0%, 100% 25%, 100% 75%, 50% 100%, 0% 75%, 0% 25%);
  clip-path: polygon(50% 0%, 100% 25%, 100% 75%, 50% 100%, 0% 75%, 0% 25%);
}
.image:before {
  background: url(http://lorempixel.com/150/150/nature/1);
}
.double:after {
  top: 8px;
  left: 8px;
  height: calc(100% - 16px);
  width: calc(100% - 16px);
  background: black;
}

/* Just for demo */

.hexagon {
  display: inline-block;
  margin: 20px;
}