.myBase {
    position: relative;
}
.myChild1 {
    position: absolute;
    top: 40%;
    left: 20%;
    z-index : 10;
}
.myChild2 {
    position: absolute;
    top: 50%;
    left: 40%;
    z-index : 20;
}
.myChild3 {
    position: absolute;
    top: 60%;
    left: 60%;
    z-index : 30;
}