<!DOCTYPE html>
<style>
canvas {
    width: 100px;
    height: 100px;
}

.positioned {
    position: absolute;
    left: 0;
    top: 0;
}
</style>
<div style="position: relative;">
    <div style="display: flex;">
        <canvas style="z-index: 100; background-color: green;"></img>
    </div>
    <canvas class="positioned" style="z-index: 50; background-color: red;"></img>
</div>