Welcome back again, Mark.
It'll help if you'll put your geographic location in your User Profile so it will remain permanently in view to help folks answer some types of questions.
I can't tell much of anything from your photo, I'm afraid. You say it shows a drain, but I don't see even that.
Basic principles involved here as far as the ceramic tile industry is concerned. All the direct bonded waterproofing membrane manufacturers I'm aware of, save one, require a primary waterproofing system (a roof) below their waterproofing system when over occupied space. That includes Schluter's system.
As I mentioned a few years ago, the only one I'm aware of that offers a direct bonded waterproofing membrane that does
not require a primary waterproofing system is the Noble Company with their
NobleDeck. That remains the case today, far as I know and that would be my first choice in your application.
You'd need an adequate structure (we know nothing about it at this point), an adequate subfloor, and then an appropriate drain and sloped mud bed. Over that you'd install your NobleSeal and tile.
While it's possible to do that small mud area in stages, I'd not recommend it. You end up with cold joints between each section and you really wanna avoid that. Granted, you can connect them with some pure Portland cement or thinset mortar and it might work OK with the NobleDeck over it, but I'd still recommend you get one good helper and do it in one try. Three by twelve feet is not beyond the capabilities of two workers who are well prepared.
The drain situation remains essentially the same. If you absolutely must have an all metal drain you can use a cast iron clamping drain or get the special stainless steel bonding flange drain from Schluter. Noble Company has a very robust surface clamping drain that is mostly metal, but it does have a PVC (I think) base. You haven't said what size drain pipe you have and that could be a factor in your selection. Again, I'd wanna talk with my code compliance people to see if some allowance can be made for a non-metalic drain in that application.
My opinion; worth price charged.