JSFiddle - React, Tailwind, and code Playground

HTML

<div id='q1'>
  <div id='q2'></div>  
</div>

CSS

#q1 {
  position: fixed;
  width: 100%;
  height: 50px;
  background-color: red;
  z-index: 0;
}

#q2 {
  position: absolute;
  top: 80%;
  border: 2px solid black;
  width: 100px;
  height: 30px;
  background-color: green;
  z-index: -1;
}