<!DOCTYPE html>

<html>
<head>
    <style>
        .container {
            position: absolute;
            top: 200px;
            left: 100px;
            perspective: 400px;
        }
        .box {
            height: 400px;
            width: 400px;
            background-color: green;
            transform: rotateY(120deg);
        }
        .clipper {
            position: absolute;
            top: 30px;
            left: 200px;
            height: 270px;
            width: 220px;
            border: 50px solid gray;
            border-top-width: 230px;
            border-bottom-width: 260px;
        }
    </style>
</head>
<body>
    <div class="container">
        <div class="box"></div>
    </div>
    <div class="clipper"></div>
</body>
</html>