JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://unpkg.com/babel-polyfill@6.26.x/browser.js"></script>
<script src="https://unpkg.com/@jurca/szn-select@1.x/polyfill/modern-ie.js"></script>
<script>
window.module = {} // required by the polyfill
</script>
<script src="https://unpkg.com/mutation-observer@1.x/index.js"></script>

<link rel="stylesheet" href="https://unpkg.com/@jurca/szn-select@1.x/szn-select-nojs.css">
<script src="https://unpkg.com/@jurca/szn-select@1.x/loader.min.js"></script>

<form action="" method="get">
  <fieldset>
    <legend>Example form</legend>

    <div class="row">
      <label for="first-select">Select one:</label>
      <span>
        <szn-select data-szn-select--standalone>
          <select name="first" id="first-select">
            <option value="banana">banana</option>
            <option value="kiwi" disabled>kiwi</option>
            <optgroup label="vegetables">
              <option value="potato">potato</option>
              <option value="onion">onion</option>
            </optgroup>
            <option value="tomato" selected>tomato</option>
          </select>
          <span data-szn-select--ui></span>
        </szn-select>
      </span>
    </div>

    <div class="row">
      <label for="second-select">Select any:</label>
      <span>
        <szn-select data-szn-select--standalone>
          <select name="second" id="second-select" multiple>
            <option value="banana" selected>banana</option>
            <option value="kiwi" disabled>kiwi</option>
            <optgroup label="vegetables">
              <option value="potato">potato</option>
              <option value="onion" selected>onion</option>
            </optgroup>
            <optgroup label="disabled optgroup" disabled>
              <option value="car">car</option>
              <option value="bike">bike</option>
            </optgroup>
            <option value="tomato">tomato</option>
          </select>
          <span data-szn-select--ui></span>
        </szn-select>
     ...

CSS

html {
  font: 100% sans-serif;
}

.row {
  display: flex;
  
  margin: 1rem 0;
}

label {
  display: block;
  
  width: 40%;
}

span {
  flex: 1 0 auto;
}