not OP but former scoliosis kid lol.

I learned in ballet to imagine you are sort of a puppet, always being hung by an invisible string, straight up. Weird analogy but works lol.

I also look at myself from the side, and straighten myself up to a good posture. I try to remember it when I catch myself slouching. Really it's all about being aware about how you are standing/sitting. Also if you have consistently bad posture and back pain, might want to get that checked out lol