Slick slider not working in a flex container

Question

I'm trying to center vertically a slick carousel (http://kenwheeler.github.io/slick/) in a column. So I use display: flex; align-items: center; on the column (container of the slick slider) but it breaks the slider.

So I have try to center the carousel with an absolute position or by using flexbox but they both breaks the slick slider.

I hope someone got a css/js/jquery solution for this issue :)

Here a fiddle of the issue : https://jsfiddle.net/victor_allegret/g3dsd78w/

(sorry I have an issue adding slick to the stack overflow snippet)

HTML :

<div class='flex-container'>

 <div class='single-item'>

  <div><h3>1</h3></div>
  <div><h3>2</h3></div>
  <div><h3>3</h3></div>
  <div><h3>4</h3></div>
  <div><h3>5</h3></div>
  <div><h3>6</h3></div>

 </div>

</div>

CSS :

.flex-container {
 /* Using flexbox */
 display: flex;
 align-items: center;
 /*----*/
 margin: 0 auto;
 padding: 40px;
 height: 500px;
 width: 80%;
 color: #333;
 background: #419be0;
}

.slick-slide {
 text-align: center;
 color: #419be0;
 background: white;
}

JS :

$(".single-item").slick({
 dots: true
});

Answer 1

Like this ? With absolute position.

.abs-container {
  position:absolute;

  height:140px;
  width:300px;
  top:50%;
  left:50%;
  margin:-70px 0 0 -150px;

  color: #333;
  background: #419be0;
}

And this with FlexBox.

.flex-container {
    position:absolute;
    top:0px;
    bottom:0px;
    width:100%;
    height:100%;

  /* Using flexbox */
    display: flex;
    flex-direction: row;
    flex-wrap: nowrap;
    justify-content: center;
    align-content: stretch;
    align-items: center;
  /*----*/

  color: #333;
  background: #419be0;
}
.flex-child {
    width: 300px;
    order: 0;
    flex: 0 1 auto;
    align-self: center;
}

HTML

<div class='flex-container'>
    <div class='flex-child'>
      <div class='single-item'>
      .
      .
      .