JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
  <div class="col-main">
    <div class=slider-container>
      <div class="slider">
        Foo
      </div>
    </div>
  </div>
  <div class="col-side">
    Side
  </div>
</div>

CSS

.container {
  display: flex;
}

.container .col-main {
  background: gold;
  flex: 1 1 100%;
  min-width: 0;
}

.container .col-side {
  background: cornflowerblue;
  flex: 0 0 15em;
}

.slider-container {
  overflow-x: scroll;
}

.slider-container .slider {
  background: repeating-linear-gradient(45deg, darkseagreen, darkseagreen 10px, dimgray 10px, dimgray 20px);
  width: 150em;
  height: 10em;
}