Sounds from the answers above like I'm on the right track after all. I've read a lot of instructions and believe I have a theoretical understanding. Some measurements in my case regarding the distance from pipes to the wall do not meet the requirements. Neither does the aforementioned requirement that incoming water pipes enter through the floor.
At least there will be a 10 cm upturn and 3 cm against the threshold. Also, a slight slope even though I'm not using leveling compound, just a bit of fine concrete.
I've also managed a 15 mm upturned edge around the pipes, which is mentioned somewhere.
The hardest part remains: welding. Wish me luck!