body {
    margin: 0;
}
.section {
    position: relative;
    height: 540px;
    box-sizing: border-box;
    background-size: cover;
}

.section:not(:first-child) {
    margin-top: -1rem;
    clip-path: polygon(0 0, calc(50% - 3rem) 0, 50% 1rem, calc(50% + 3rem) 0, 100% 0, 100% 100%, 0 100%);
}
.section:not(:last-child) {padding-bottom: 1rem;}

.s1 {background-image: url(https://picsum.photos/1920/541);}
.s2 {background-image: url(https://picsum.photos/1920/542);}
.s3 {background-image: url(https://picsum.photos/1920/543);}
.s4 {background-image: url(https://picsum.photos/1920/544);}

.box {
    position: absolute;
    top: 50%;
    left: 50%;
    translate: -50% -50%;
    background-color: white;
    padding: 1rem;
    border: 3px solid rgba(0, 0, 0, 0.1);
}