Fostering students' mathematical creativity is important for their understanding and success in mathematics courses as well as their persistence in STEM, but it necessitates intentional instructional actions, such as designing and implementing tasks that have the potential to foster creativity. As teaching innovation requires support for instructors who implement them, we developed a creativity-fostering task design framework that can be used by instructors of undergraduate mathematics courses. In this paper, we share this framework and its research-based development process. The framework includes research-based task features and aligns with the Creativity-in-Progress Reflection (CPR) on problem-solving, a formative assessment instrument. We share two creativity-fostering task samples for Calculus 1 courses as we notice that this course could be enhanced with such tasks. We also discuss ways in which Calculus 1 instructors utilized task features and framework as they designed their own tasks. We observed that the multiple answers and open-ended features of creativity-fostering tasks were frequently incorporated in instructors' tasks; meanwhile, the framework provided opportunities for instructors to be intentional about creating tasks that incorporate mathematical actions such as making connections and taking risks.