We can achieve the same result as in example 2 and 3 declaring all four values with the grid-area property. Again values are separated with a /. The order of the values is row-start/column-start/row-end/column-end.

Credit to gridbyexample.com for inspiring this example.

[fl_row] {
    display:grid;
    grid-gap: 10px;
    grid-template-columns: 1fr 1fr 1fr;
}
[fl_row] .a {
    grid-area: 1 / 2 / 2 / 3;
}
[fl_row] .b {
    grid-area: 2 / 2 / 3 / 3;
}
[fl_row] .c {
    grid-area: 2 / 3 / 3 / 4;
}
[fl_row] .d {
    grid-area: 1 / 1 / 2 / 2;
}
[fl_row] .e {
    grid-area: 2 / 1 / 3 / 2;
}
[fl_row] .f {
    grid-area: 1 / 3 / 2 / 4;
}

A

B

C

D

E

F