Here are some strategies which will help you to deliver good feedback, that can make learners think without risking demoralizing them. Do not forget that in order for the learners to think about the feedback, it is also very useful be make them active in the feedback process, for example by asking questions...

The Sandwich feedback technique : the goal is to give a balanced feedback, by surrounding constructive remarks with positive comments. Following this technique, you should first give a positive comment, then follow with a constructive remark to end with another positive comment.

The EDGE model : The EDGE model also aims at providing a balances feedback, while giving it a clear and smooth structure. EDGE stands for Explain, Describe, Give, End positively. With this model, you are encouraged to first Explain the situation, and then Describe the behaviour that led to the feedback. You should then Give a specific feedback, for example a recommendation or tips. Finally, it is important to End positively.

The DESC technique : This techniques aims at making sure you deliver a structured feedback based on good practices. DESC stands for Describe, Express, Specify and Consequence. Following this technique, you should first Describe the situation as it is, Express how it makes you feel, Specify your expectations or what you would expect to change, and Explain the consequence if the situation continues as it is.

The GROW model : with this model, as for with the DESC technique, we aim at delivering a state of the art feedback without omitting any important aspect. GROW stands for Goals, Reality, Options and Wrap-up. Meaning that when using this model, you should first expose the Goals of the person, than compare them to the Reality ( ie the current situation). You should then discuss Options with the person before Wrapping-up by summing the discussion and putting forward the key takeaways.

The STAR method : this method aims to ensure that the feedback is specific and relevant to a given situation. STAR stands for Situation, Task, Action, Result. When using this method, you should first expose the Situation which led to the feedback, and the Task asked. Then you can discuss the Action taken by the learner, and finally the Result they got.

Source : https://www.getjop.com/blog/feedback-techniques-and-method