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Bootstrap class: .align-self-*-baseline

<div class="align-self-baseline">Aligned flex item</div>

<!-- responsive variations -->
<div class="align-self-sm-baseline">Aligned flex item</div>
<div class="align-self-md-baseline">Aligned flex item</div>
<div class="align-self-lg-baseline">Aligned flex item</div>
<div class="align-self-xl-baseline">Aligned flex item</div>

Preview

Flex item 1
Aligned flex item
Flex item 3