The best way to know how you do something without a doubt is to be able to see yourself doing it!
Get your students to record each other for 30 seconds to 1 minute with the video function of their smart phones so they can see and hear for themselves how they come across when they speak English.
Students can spend 5 minutes to write down 6-8 questions that they would like to ask their partner. This can be a free activity or lexis, grammar determined by the teacher.
Students then interview each one at a time while simultaneously recording their partner using their smart phones.
During the play back, students are encouraged to think about their pronunciation and their voice projection. They decide whether they speak clearly or if there is something that could be improved.
Another variation would be for the teacher to give the students a text containing sounds that are difficult for their learners, in order for the learners to see how they are pronouncing the sounds and if they could do it differently.
If the class is large, pairs could be grouped in fours for the playback stage to compare and contrast pronunciation with more peers.
If you try this activity, let me know how it goes in the comments!