If I may add a few things that helped me a lot.

Esther Gokhale's book.
https://www.amazon.com/Steps-Pain-Free-Back-Solutions-Shoulder/dp/0979303605

Talks about how to sit, how to stand, how to walk, how to lay, etc. Once you get that, you can start applying it 24/7 instead of the usual "do these shitty exercises with a rubber bands twice a day" that physiotherapists prescribe. NO ONE DOES THOSE. haha

The one thing I would caution about her approach is that she OCDs on neurtral spine. Make sure you do plenty of mobility exercises during your day to make sure you keep a healthy spine :)

Final thing I'd say is that to position your pelvis (the "first/huge/ vertebrae) simply squeeze your glutes. Instead of over thinking it, just squeeze dat ass and voila, pelvis aligned and ready to stack the rest on top. This is from Kelly Starret's book Becoming A Supple Leopard.