for 3:

    + - - - - - - - - - - - +
    | m m 3 m m 3 m m 3 m m |
    | m 3 3 m 3 3 m 3 3 m 3 |
    | 3 3 3 3 3 3 3 3 3 3 3 |
    | m m 3 m m 3 m m 3 m m |
    | m 3 3 m 3 3 m 3 3 m 3 |
    | 3 3 3 3 3 3 3 3 3 3 3 |
    | m m 3 m m 3 m m 3 m m |
    | m 3 3 m 3 3 m 3 3 m 3 |
    | 3 3 3 3 3 3 3 3 3 3 3 |
    | m m 3 m m 3 m m 3 m m |
    | m 3 3 m 3 3 m 3 3 m 3 |
    + - - - - - - - - - - - +

for 4:

    + - - - - - - - - - - - +
    | m m 4 m m 4 m m 4 m m |
    | m m 4 m m 4 m m 4 m m |
    | 4 4 4 4 4 4 4 4 4 4 4 |
    | m m 4 m m 4 m m 4 m m |
    | m m 4 m m 4 m m 4 m m |
    | 4 4 4 4 4 4 4 4 4 4 4 |
    | m m 4 m m 4 m m 4 m m |
    | m m 4 m m 4 m m 4 m m |
    | 4 4 4 4 4 4 4 4 4 4 4 |
    | m m 4 m m 4 m m 4 m m |
    | m m 4 m m 4 m m 4 m m |
    + - - - - - - - - - - - +

For 6:

    m m m m
    m 6 6 m
    m 6 m m
    m m m m