Doubtless there are many arching stone doorways that have been created from this lesson, but I figured I’d share mine after going through it, laying out my “bricks”, and then carving them up 
Mainly, all of this is done by combining the bisect tool, the knife tool, some edge looping, and a displacement modifier driven by a noise texture – after applying the initial Mirror modifier that we started with. So many ways to do things – and I enjoyed all the tidbits that I was able to pick up by seeing how Grant did it as well 
On to the next lesson!