Hi Kyle,

Yes, you install the base first. Contact Onyx for installation instructions (they should be available on their website). We have had two cultured marble bases made (similar to Onyx for your purposes). The first one looked something like the one you have posted, unfortunately, I seem to have lost all my pics from that year...? But here is one from the present reno. The base is made slightly differently, ie there is only a curb on the entrance side, and the other three sides are just thin walls that the cement board, and then the tile go over. The tile was laid to end nearly at the bottom of the pan.

Hope this helps.

Thanks Raehelen, that does help,

I also contacted Onyx directly, and they referred me here: www.onyxcollection.com/shower-installation-tutorial.html

(I had watched their video tutorials and read their installation PDF, but somehow overlooked this page, which seems to be just what I was looking for.)

Thanks again