JSFiddle - React, Tailwind, and code Playground

HTML

<ul class="thumbnails">
<li class="thumbnail"></li>
<li class="thumbnail"></li>
<li class="thumbnail"></li>
<li class="thumbnail"></li>
<li class="thumbnail"></li>
<li class="thumbnail"></li>
<li class="thumbnail"></li>
<li class="thumbnail"></li>
</ul>

CSS

.thumbnails {
  display: flex;
  margin: 0;
  padding: 0;
  list-style-type: none;
  flex-flow: row wrap;
  width: 640px;
  height: 400px;
  justify-content: space-between;
}

.thumbnails::after {
  content: "";
  margin-right: auto;
}

.thumbnail {
  width: 100px;
  height: 100px;
  background: #ccc;
  border: 1px solid #000;
}