The flipped classroom is a pedagogical technique where we educators push students to do factual learning before class so that we can use class time to focus on application and, thus, go deeper into the content. There is no need for a platform to do this. However, you could use a wide range of platforms (a learning management system (LMS), a content hosting website, etc.). So, a little clarity from you would help us to give you better quality answers.
Overall, to use the UTAUT model, I would presume that you are testing user acceptance of some technology, for example, a new LMS that you are using for the flipped classroom content. There are lots of journal articles that have used the UTAUT. So, one answer would be to read a few of those articles, see how they applied it, and then follow their process.
It will likely involve: Creating a questionnaire, getting the students to answer the questionnaire, and then analyzing the results in the light of existing literature.