This 20-30 minute exploration of designing a HyFlex course was released in 2021 by OneHE and is available to anyone for free (uses a CC license). This micro-course may be a good general starting point for someone learning about designing a HyFlex course.
“This course has been developed with Dr. Brian Beatty, Associate Professor, San Francisco State University, USA. For more information on it and to get started, go to the first lesson, ‘Welcome to the course’. The contents of the course are listed below. This course includes several short videos and should take approximately 20 minutes to complete.”