A, 'keep it simple' moment, (&, no, I do not use a 'twist 'd cord' figure 8, (nttawwt) it is just a clear example)
As pictured, this is fine, but as a general method I would be careful about teaching it. As shown it works because of the ring/mallion on the anchor. In a situation where there is just a big loop of cord or webbing, the carabiner can pass over the loop. Hence the need to clip the carabiner to the other line.