Some solutions with all values from 0 to 6 for 7X7X7
........2..............0..............0..............1..............0
.......0.0............1.1............2.2............0.2............0.0
......0.5.0..........1.6.1..........0.4.0..........2.4.0..........0.5.0
.....0.3.0.0........0.1.1.0........3.2.2.0........0.2.2.0........0.0.3.0
....1.1.2.0.2......0.2.1.3.0......0.0.1.1.1......0.0.1.1.1......2.0.2.1.1
...1.6.1.2.4.2....2.4.2.0.5.0....0.5.3.1.6.1....0.5.3.1.6.1....2.4.2.1.6.1
..0.1.1.0.2.0.0..0.2.0.3.0.0.2..2.0.0.0.1.1.0..2.0.0.0.1.1.0..0.0.2.0.1.1.0