Unity 3D boxgeneration algorithm - random bottom -> top

Hangar.cs

        public void GenerateCrates(int crateCount)
        {
            var crateSize = Crate.GetComponent<BoxCollider>().size;
            var bounds = SpawnBounds.bounds;

            var maxCrates = bounds.size.x * bounds.size.z * bounds.size.y;
            Assert.IsFalse(crateCount > maxCrates, "Cargo hold cant hold that much crates!");

            var bottomMin = bounds.min + crateSize / 2;

            var possiblePositions = new List<Vector3>();
            for (var x = bottomMin.x; x < bounds.max.x; x = x + crateSize.x)
            {
                for (var z = bottomMin.z; z < bounds.max.z; z = z + crateSize.z)
                {
                    for (var y = bottomMin.y; y < bounds.max.y; y = y + crateSize.y)
                    {
                        possiblePositions.Add(new Vector3(x, y, z));
                    }
                }
            }

            var positionsToGenerate = new List<Vector3>();

            for (int i = 0; i < crateCount; i++)
            {
                var nextPosition = possiblePositions[Random.Range(0, possiblePositions.Count - 1)];

                nextPosition = possiblePositions.Where(pos => pos.x == nextPosition.x && pos.z == nextPosition.z)
                    .OrderBy(x => x.y)
                    .FirstOrDefault();

                positionsToGenerate.Add(nextPosition);
                possiblePositions.Remove(nextPosition);
            }

            foreach (var position in positionsToGenerate)
            {
                Instantiate(Crate, position, Quaternion.identity);
            }
        }