I'm left handed too. I can't work out clockwise and anti and so on. Also have problems looking at photos and deciding which hand side is which.
Anyway my method, hold buckle in right hand, thread belt with my left hand from my left, around the back to the right
Do up buckle.
I lost a lot of weight, cycling helped but cutting hidden sugar and portion size made the real difference.
Found those belts composed of woven strands of elastic make the adjustments easy.
Any one got a mnemonic for the left hand right hand dilemma?