I built up the intuition 10 years before the 2021 post -- it's a while back so my memory is fuzzy. But once you've got the ecliptic, you're most of the way there: you can visualise where the Earth is in its orbit based on the time of year, and Sgr A* is in a fixed direction relative to the Solar System.

Build up to it, a few minutes waiting for the bus every day, checking your sense with an app like Star Walk... it's relatively straightforward. I've learnt harder things I'm sure.