how to align the text at very centre of the div element in flex bx code example

Example 1: how center content in css by using flex

display: flex;
    width: 60%;
    justify-content: center;
    margin: 0 auto;

Example 2: how to horizontally center header at the top of page with flexbox css

.box.flex {
  display: flex;
  justify-content: center;
}