The usual way to tile a custom shower base is to install a liner and adjustable drain, and then pour a concrete shower base. After the concrete drys you tile the floor. This process is slow and time consuming, but yields a good result when you use an experienced tile setter.

The Schluter Shower System is more expensive, but the job is done in a fraction of the time that it would take to finish it using traditional methods. The end result is perfect. See photos below.

The shower base comes in pre-made sizes, but they can be trimmed down to fit your shower.
You make your cuts with a utility knife, and then break off the portion that you don’t need.
Apply the Schluter mortar on top of your subfloor and place your cut shower base.

Reinforce the corners with the Schluter waterproof membrane.
Installing Schluter drain.
Shower base complete and ready to be tiled!