<!DOCTYPE HTML>
<html>
<body>
<style>
p { flex-grow: 1; }
</style>
<fieldset style="overflow:hidden; width:200px; height:200px;">
<legend>Legend</legend>
<div style="display:flex;">
<p>X
<p>X
<p>X
<p>X
<p>X
<p>X
<p>X
<p>X
<p>X
<p>X
<p>X
</div>
</fieldset>
<fieldset>
<legend>Legend</legend>
<div style="display:flex;">
<p>X
<p>X
<p>X
<p>X
<p>X
<p>X
<p>X
<p>X
<p>X
<p>X
<p>X
</div>
</fieldset>
</body>
</html>