In this study, a new model termed as "Flexible Inquiry Based Science Teaching", which is developed using the framework of the inquiry approach is proposed. Science teachers (n=2) who participated in the study were instructed on the inquiry approach and their in-class activity applications were examined. The "electricity module" in the annual plans of 5th and 6th grades was chosen to be the subject of the activity designs and applications. Activities were applied in various classes in the same grade level, which allowed activity designs to be improved by performing repetitive applications based on the feedbacks. Due to the "flexible" nature of the FIBST model, teachers were able to design and apply activities according to the varying conditions of the teaching environment. At the end of the process, they gained the ability to adapt any activity into an inquiry-based activity.