JSFiddle - React, Tailwind, and code Playground

HTML

<flex-container>
    <flex-spacer></flex-spacer>
    <flex-item>
	    <flex-item></flex-item>
	    <flex-item></flex-item>
	    <flex-item></flex-item>
    </flex-item>
    <flex-footer>
      this is the footer element<br />
      this is the footer element<br />
    </flex-footer>
</flex-container>

CSS

flex-container {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    border: 4px solid blue;
    height: 300px;
    width: 300px;
}

flex-container > flex-spacer {
    margin-top: auto;
    visibility: hidden;
}

flex-container > flex-item {
    display: flex;
}

flex-container > flex-footer {
    margin-top: auto;
    margin-bottom: auto;
}

flex-container > flex-spacer,
flex-container > flex-footer {
    border: 4px solid chartreuse;
}

flex-container > flex-item > flex-item {
    border: 4px solid aqua;
    height: 50px;
    width: 50px;
    margin: 0 5px;
}