C++ :: Concatenate Two 2-dimensional Int Arrays Into One Larger 3-dimensional Array

How can I concatenate two 2-dimensional int arrays into one larger 3-dimensional array. This question is also valid for the 3-dimensional vectors. I know the command for the one dimensional vector as:

std::vector<int> results;
results.reserve(arr1.size() + arr2.size());
results.insert(results.end(), arr1.begin(), arr1.end());
results.insert(results.end(), arr2.begin(), arr2.end());

and for the one dimensional array as:

int * result = new int[size1 + size2];
copy(arr1, arr1 + size1, result);
copy(arr2, arr2 + size2, result + size1);

But I do not know how to make a 3-dimensional array or vector.