You can see that the toilet is a little rough on the bottom.
I used some Kerdi and made a "Kerdi Water Closet Kit". The kit was simple enough to make. I cut small sections of Kerdi out and siliconed them to the bottom of my toilet. I did this first and used a small amount of White Silicone to affix the Kerdi to my toilet.
Thin strips of Kerdi set with White Silicone.