Wrapping criticism between two compliments teaches people to ignore your compliments. After a few rounds, every piece of praise sounds like the warm-up to bad news.
Give positive and corrective feedback separately and specifically. Describe the situation, the behaviour you saw and the impact it had, then ask what the other person saw. The question matters more than the delivery: it turns a verdict into a conversation.
Feedback is a gift only when the person giving it is genuinely curious about the answer.
Aim for a ratio of roughly three specific acknowledgements to every correction over a month, not within a single conversation.