The paper presents a conceptual framework for flexible learning design, specifically focusing on the context of the Flipped Classroom (FC). The aim is to provide a comprehensive understanding of flexibility in learning environments and course designs, as well as explore emerging flexible modalities. The paper also underlines the theories underlying flexible learning design and discusses the implications and considerations associated with implementing such approaches. The introduction highlights the role of flexibility in education and introduces key discussions. The conceptual framework section defines flexibility and explores its various dimensions, establishing a foundation for the related arguments. Next, the paper discusses the theories that underpin flexible learning design, providing insights into the pedagogical principles and approaches that support this educational paradigm. It further explores flexible learning environments, addressing the key elements and characteristics that contribute to their effectiveness. The subsequent sections elaborate on the specific aspects of flexibility in different learning settings. It explores flexibility in F2F, blended, and online learning contexts, highlighting the unique considerations and strategies for each modality. This is followed by the presentation of emerging flexible modalities, discussing their potential benefits and challenges. The paper also emphasizes the critical role of flexibility in teaching and learning exploring how flexibility impacts what and how students learn, the delivery of instruction, didactic strategies for organizing learning activities, provision of learning resources, and the assessment and evaluation process. Furthermore, the concept of flipped learning is discussed as a flexible design, showcasing its potential as an effective approach to flexible learning. It provides practical suggestions and potential strategies for implementing flexible design within the framework of flipped learning. The literature review section synthesizes existing research on students' and teachers' perceptions of the effectiveness of the FC where the benefits and challenges associated with flexible learning approaches are explored and discussed. The paper concludes with implications and considerations for implementing flexible learning design with a discussion on the importance of student agency in taking control of the learning experience, overcoming institutional barriers, balancing planned and spontaneous flexibility, and designing for students with special needs. The paper offers a comprehensive exploration of flexible learning design within the context of the flipped classroom. It provides valuable insights into the conceptual framework, theories, practical strategies, and implications associated with implementing flexible learning approaches. The findings and recommendations presented in this report aim to inform teachers, educators, policymakers, and researchers in their efforts to promote effective and adaptable learning experiences while designing a flipped learning in their classroom.