JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
  <div class="button-wrap">
    <div class="button-group">
    <button>[]</button>
    <button>X</button>
    <button>-</button>
   </div>
  </div>
 

 <div class="main-box"></div>
 <div class="myfooter"> </div>
</div>

CSS

.container{
  width: 500px;
  height: 500px;
  background: pink;
  
  display: flex;
  justify-content: flex-end;
  flex-wrap: wrap;
}
.button-wrap {
  display: flex;
  flex-basis: 100%;
}
.button-group {
  background: lightblue;
  align-self: flex-start; /* Not working!*/
  padding: 5px 10px;
}

.main-box {
  width: 450px;
  height: 300px;
  background: lime;
  align-self: center;
}

.myfooter {
  width: 50%;
  height: 10%;
  background-color: black;
}