append matrix to stl matrix (2d std::vector)

Is this the way to append rows (matrix) to a matrix?

#include <vector>
#include <memory>
using std::vector;

int size = 4; // width;
int chunk = 2; // high
int main(int argc, char const *argv[]) {
    vector<vector<int>> m(10, vector<int>(size));

    auto func = []() {
        vector<vector<int>> n(chunk, vector<int>(size));
        return n;
    };
    int j = 0;
    for(int i = 0; i < 5; i++) {
        auto n = func();
        for(auto &row : n) m[j++] = row; // append rows
    }
}

I hoped it will be possible to just m.push_back(n).