How add spaces between Slick carousel item

I want to add space between two slick carousel items, but not want the space with padding, because it's reducing my element size(and I don't want that).

enter image description here

    $('.single-item').slick({
        initialSlide: 3,
        infinite: false
    });

.slick-slider {
    margin:0 -15px;
}
.slick-slide {
    padding:10px;
    background-color:red;
    text-align:center;
    margin-right:15px;
    margin-left:15px;
}

<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/js/bootstrap.min.js"></script>
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css" rel="stylesheet"/>
<script src="http://cdn.jsdelivr.net/jquery.slick/1.5.0/slick.min.js"></script>
<link href="http://cdn.jsdelivr.net/jquery.slick/1.5.0/slick.css" rel="stylesheet"/>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.0/jquery.min.js"></script>
<div class="container">
    <div class="row">
        <div class="col-sm-12" style="background-color:gray;">
            <div class="slider single-item" style="background:yellow">
                <div>1</div>
                <div>2</div>
                <div>3</div>
                <div>4</div>
                <div>5</div>
                <div>6</div>
            </div>
        </div>
    </div>
</div>

Somehow I am getting space from both side, I am trying to remove that.

Solution

Yup, I have found the solution for dis issue.

Create one slider box with extra width from both side( Which we can use to add item space from both sides ).
Create Inner Item Content with proper width & margin from both sides( This should be your actual wrapper size )
Done