There are many ways to create fusion flows. A simple way is to do the first half of your practice in yin mode, and the second half in yang mode. Or vice versa. These are just two individual, but short yoga classes combined together. When I first started teaching Yin Yoga in Vancouver B.C., very few people had ever heard of Yin Yoga, so I snuck it into my Hatha classes: I would start with 30 minutes of Yin, and take the time in the postures to explain to the students why it was so valuable for them (the benefits of the practice) and then finish the class with 30 minutes of yang practice. You could reverse this for a late night class and start with yang and end with yin, so the students are ready for bed, not all jacked up.
More complex is to work yin and yang postures in between each other, as shown in this Yin/Yang Fusion flow
, which is a combination of yin and yang poses woven together. Here the philosophy is to interlace chunks of yin practice with chunks of yang: Do NOT go 5 minutes yin, 1 minute yang, 2 yin, 3 yang, etc. Instead offer chunks of 10 minutes of all yin and then 10 minutes of all yang, etc. You could also visit my video page and click on the Yin/Yang Fusion: Working the Whole Body
link and watch a preview of a yin/yang class I offer on Gaiam. It is basically the flow described above.
It would be interesting to hear other teachers' experiences.