文字を□で囲う

<h3 class=""><span class="span1">お</span><span class="span1 span2">客</span><span class="span1">様</span><span class="span1 span2">の</span><span class="span1">声</span></h3>

.page-id-5 #content.l-content #main_content .section5 h3 {
    font-weight: 900;
    font-size: 3.646vw;
    display: flex;
    justify-content: center;
    line-height: 1.04;
    margin-top: 0.4em;
}

.page-id-5 #content.l-content #main_content .section5 h3 .span1 {
    background: #fff;
    color: #000;
    display: flex;
    justify-content: center;
    align-items: center;
    width: 1.6em;
    height: 1.6em;
    border: 1px solid #000;
}