JSFiddle - React, Tailwind, and code Playground

HTML

<div id="button">Text</div>
    <div id="box">
        Text
    </div>

CSS

#button{
    position: absolute;
    background-color: rgb(186,200,227); 
    border-bottom-left-radius: 20px;
    border-bottom-right-radius: 20px;
    border-top-left-radius: 20px;
    border-top-right-radius: 20px;   
    width: 410px;    
    padding: 12px;
    padding-top:8px;
    padding-bottom:8px;
}

#box {
    position: absolute ;
    top: 84px ;
    left: 80px ;
    width: 350px ;
    height: 200px ;
    border: 3px dotted green ;
}

#box:before {
    position: absolute ;
    content: "" ;
    width: 50px ;
    height: 50px ;
    left: -55px ;
    top: -53px ;
    border-left: 3px dotted green ;
    border-bottom: 3px dotted green ;
    background: #fff;
    border-top : 3px solid rgb(186,200,227);
}