There are a lot of ways to build a shower pan. There are a lot of ways to waterproof a shower.
And there are a lot of people in the world that would like you to believe that in order to build a solid, totally custom leak-free shower, you need to spend a silly amount of money and use approximately 47 different layers of waterproofing products.
The thing is...I've demo'd enough bathrooms in really, really old houses to know different; if the work is good, old-school methods work just fine (and cost way, way less than the newer products on the market). All the new waterproofing liquids and membranes and products and systems...it's like they're made simply as a license to do half-assed work. They're good products, and there's a time and place to use them...but they're not nearly as essential as a lot of people think they are. And even though there are a lot of contractors and tradespeople that frown upon some of the old-school ways of doing things, for some goofy reason, I really enjoy building shower pans - when the opportunities present themselves - and building them the old-fashioned way (although...I dunno that they were using vinyl shower pan liners 100 years ago).
Day 2 @ the current bathroom shower renovation project included beefing up the subfloor a bit, adding in some blocking so I had a form of sorts for the shower pan (and something to nail the liner to), and then throwing down the sand cement pre-slope, which is the first of two sand cement mixes used in building shower pans.
The sand cement mix is pretty much just that, a combination of sand, portland cement and water (roughly 5 parts sand to 1 part cement) that I mix up on-site to the consistency of, well, wet sand. It's way, way less soupy than the concrete you're probably used to seeing in flatwork and foundations, and is essentially packed into whatever shape one wants, vs. formed, poured and then screeded or floated out. The purpose of the pre-slope is to build a pan that slopes, roughly 1/4" per 1', towards the shower drain from all sides, and is essentially what starts to dictate just how well water will drain in the shower.
It takes a little time and effort to get the slope just right, especially when you don't do that type of work every single day, but I'm always pretty excited to see the end result, because I get to say "I made that", instead of "I bought that and threw a few screws in it".
Here's a pretty quick and dirty look at what today's work looked like: