… not that I’m very successful at learning it!
The Catamount Trail Association has this page to offer about Using the Rear Foot Actively. Its strength for me and presumably others is that it addresses Alpine skiers and their acquired instincts rather well. Note: This rear foot business isn’t a detail to investigate once you have grasped the basics. It very much is the basics, which is why a lengthy and sympathetic description is so vital to us conventional skiers.
Then, if you really want, you can also watch this video – which is well and truly about learning telemark the hardest way: on thin cross-country skis made for groomed tracks. That said, if cross-country skis are the only Nordic equipment you possess (which is often the case) the clip may be worth watching.