<!DOCTYPE html>
<style>
    .clip {
        width: 100px;
        height: 100px;
        padding: 20px;
        border: 20px solid rgba(0, 0, 0, 0);
        border-radius: 30px;
        margin: 20px;
        background-color: blue;
        -webkit-clip-path: stroke-box;
    }
</style>
<body>
    <div class="clip"></div>
</body>