SCSS

HTML

<ul class="content">
            <li 
                v-for="(result, key) in results" 
                :key="key"
            >
                <div class="checkbox">
                    <input type="checkbox" />
                </div>
                <div class="container">
                  content<br>
                  content<br>
                  content<br>
                  content<br>                  
                </div>
            </li>
        </ul>

SCSS

ul {
    &.content {
        list-style-type: none;
        margin: 0;
        padding: 0;
    }
    li {
        // align-items: center;
        display: flex;
        // flex-direction: row;
        // overflow: auto;

        & + li {
            border-top: 5px solid black;
        }

        div.checkbox {
            // height: 100%;
            // flex: 1;
            // align-items: stretch;
            // flex-shrink: 0;
            
            display:flex; // Add this
                        
            &:hover {
                background-color: green;
            }
            input[type=checkbox] {
    
                align-self: center; // Add this
            }
        }

        div.container {
          
            
            padding: 10px;
            width: 100%;
            &:hover {
                background-color: lighten(lightblue, 10%);
                cursor: pointer;
            }
        }

        header {
            font-size: 125%;
            font-weight: bold;
            .small {
                font-size: 80%;
                font-weight: normal;
            }
        }        
    }
}