How to waterproof shower?

I have a question about waterproofing our shower. We have a pre-slope, then the PVC liner, then the final mud bed. We are going to use the Aquadefense liquid waterproof membrane. We installed our cement board after finishing the final mud pan. There is about 1/8"-1/4" gap between the bottom of the cement board and the top of the mud pan. Can I use the alkali resistant tape to seal the gap, and then thinset over top of that? Or should I use the waterproofing fabric and paint over that with the Aquadefense? Also, I've seen some people use the liquid waterproof over their entire finished mud pan, but many people are saying not to do that because it can create a "mold sandwich". Can I just waterproof around the perimeter of the mud pan a few inches so that I avoid creating this "mold sandwich" but still have the gap sealed and waterproofed?