How to make border with square on corners?

Question

How to make border with square on corners? And break one of the borders. Like on the image.

I did it with four additional blocks but I guess there might be a better way. And I don't know how to break outer border.

:root {
  --size: 8px;
  --r: -3px;
}

.wrapper {
  position: relative;
  border: 1px solid black;
  margin: 25px auto;
  padding: 2px;
  width: max-content;
}

.inner {
  padding: 15px 25px;
  border: 1px solid black;
}

.conner {
  position: absolute;
  height: var(--size);
  width: var(--size);
  background-color: black;
}

.bottom {
  bottom: var(--r);
}

.right {
  right: var(--r);
}

.top {
  top: var(--r);
}

.left {
  left: var(--r);
}

<div class="wrapper">
  <div class="inner">qwerty</div>
  <div class="conner top left"></div>
  <div class="conner top right"></div>
  <div class="conner bottom left"></div>
  <div class="conner bottom right"></div>
</div>

Answer 1

You can use border-image property in CSS.

Follow these steps:

1. Create an image as below:

2. apply border-image on .wrapper and provide the image url. Read more about border-image : https://developer.mozilla.org/en-US/docs/Web/CSS/border-image

.wrapper {
  height: 160px;
  width: 250px;
  border-style: solid; 
  border-image: url(https://i.sstatic.net/2RoPg.png) 12 / 6 stretch;
  position: relative;
  box-sizing: border-box;
}

.inner {
  height: 100%;
  width: 100%;
  position: relative;
  display: flex;
  justify-content: center;
  align-items: center;
  box-sizing: border-box;  
}

<div class="wrapper">
  <div class="inner">QWERTY</div>
</div>