CSS

Hide scrollbar

.container {
    -ms-overflow-style: none;  /* Internet Explorer 10+ */
    scrollbar-width: none;  /* Firefox */
}
.container::-webkit-scrollbar { 
    display: none;  /* Safari and Chrome */
}

Flex scrollable column

<style>

.container {
    display: flex;
    flex-direction: column;
    height: 100%;
    width: 500px;
    background-color: magenta;
}

.content {
    flex: 1;
    overflow-y: scroll;
    display: flex;
    flex-direction: column;
    align-items: center;
}

.thing {
    font-size: 64pt;
    color: yellow;
}

html, body {
    height: 100%;    
}

header {
    background-color: chartreuse;
}

footer {
    background-color: cyan;
}
</style>
<div class="container" >
    <header id="header" >This is a header</header>
    <div class="content" >
        <div class="thing">asdf</div>
        <div class="thing">asdf</div>
        <div class="thing">asdf</div>
        <div class="thing">asdf</div>
        <div class="thing">asdf</div>
        <div class="thing">asdf</div>
        <div class="thing">asdf</div>
        <div class="thing">asdf</div>
    </div>
    <footer id="footer" >This is a footer</footer>
</div>

Floating corner debug panel

.debug-panel {
    border: "1px dashed magenta";
    padding: "6px";
    background: "lightcyan";
    position: "fixed";
    width: "600px";
    overflow: "auto";
    bottom: 0;
    right: 0;
}