I deal with a lot of self-hate as well. A sort of running narrative in my head that's just extremely negative. So what my therapist has been trying to get me to do is to interrupt it. Whenever I notice myself actively hating on something about me, I instead say "I love and accept myself".
I totally laughed about it when she told me to do that. I think I kind of pissed her off a little tbh, but sorry, that's some hippy-dippy stuff to run around telling yourself. But I gave it an honest shot anyways and was quite surprised to find that it actually works. Even if you don't believe it when you say it (because how can you, if you did you wouldn't have the self-hate problem, right?), it still manages to sort of derail the negative train of thoughts, at least temporarily. So you have to keep up on it, and you have to be careful to not start adding qualifiers "I love and accept myself, but..."
You do have value as a person.
It's also useful to increase that value. Doing for others, however small it may be, makes us feel better about ourselves. So be selfless for completely selfish reasons!