Box 1: grid-row: 1; grid-column: 1;
Box 2: grid-row: 1; grid-column: 2;
Box 3: grid-row: 1; grid-column: 3;
Box 4: grid-row: 2; grid-column: 1;
Box 5: grid-row: 2; grid-column: 2;

Box A: grid-row: -5; grid-column: -6;

Box B: grid-row: 5; grid-column: 6;

Test Box: grid-row: -1; grid-column: -1;