Looking at a tournament live-stream today, I noticed how some players have good posture, and most others... do not.

Examples of bad and good posture:


What are your tips & tricks for having a better posture on the board (OTB)?

Given that OTB tournaments have typically their own furniture - different height of chair/table, with only the top-level tournaments typically providing adjustable chairs - or being played on the floor on a tatami - how does one manage to make the least amount of improvements so as to be able to sit properly?
Is there a procedure/checklist to follow, a bit like when gathering the required things to build a campfire?
A simple example is asking for a pillow to sit on to adjust a little bit one's base height - but surely there may be other things to do.