.f1 {
    grid-column: 1 / span 2;
    grid-row: 1 / span 4;
}
.f2 {
    grid-column: 3 / span 2;
    grid-row: 1 / span 2;
}
.f3 {
    grid-column: 3 / span 2;
    grid-row: 3 / span 2;
}