Hi All - I'm a strong advocate for the idea that correct spinal posture, translates to proper oral and tongue (mewing) posture and ultimately better results. To improve the face you need an underlying skeletal-musculature structure that will support the improved cranium. I've seen links to videos darted all over the forum with correct posture instructions many of which I already use, so I thought I'd consolidate some of the most pertinent ones below so that they're easily accesible by everyone (i'm assuming direct links are allowed on threads?):

Full body posture correction by AthleanX (a personal favourite of mine with the resistance bands!):

https://www.youtube.com/watch?v=TQqgf8kB6R8&t=0s&index=26&list=PLWrirXEOSTIGVwyt-bppa4lPS168Jw3_L

fixing forward head posture by Jeremy Ethier:

https://www.youtube.com/watch?v=wQylqaCl8Zo&t=0s&index=12&list=PLWrirXEOSTIGVwyt-bppa4lPS168Jw3_L

Another by Jeremy Ethier. This time, fixing your anterior pelvic tilt  - an ideal technique for those who are sat down for 8hours or more:

https://www.youtube.com/watch?v=2NZMaI-HeNU&t=0s&index=14&list=PLWrirXEOSTIGVwyt-bppa4lPS168Jw3_L

I also purchased a body posture corrector, which is an adjustable  Velcro strap based vest worn over the shoulder with a hard plate on the back. While sat down working I feel it pulling the shoulders back, and the sternum out (due to the plate push at the back mid-section of the spine). All involuntary of course, which is ideal for individuals who really don't have the time to consciously apply correct posture or simply forget when caught up in the daily demands of life - over time I started feeling muscle sores behind the shoulders and the upper spine, an indication that it's recruiting muscles to hold the new form. I've had it for 2 weeks and it has helped a lot.