Walk-in Shower, Anyone built one? Looking for tips

I will be doing full bathroom renovation, and the plan is to build a walk in shower due to the layout of the bathroom to give more open space and I don't want any nasty plastic stuff in my home so want to build something nice from scratch.
I have changed few toilets/sinks in past where I have needed them but that's where my plumbing/bathroom expertise ends so I want to try my hand in this

The plan is to build something like this, where there is only 1 glass panel hanging, and a tiled curb on the floor to keep the water inside.
however I have got a few questions maybe someone could answer

1. I understand you need to waterproof everything, I saw some videos where they either put against wall/floor some special panels + tape-join the corners and paint with some special solution to waterproof everything or either attach some membrane and just tile over it, I have no idea what products are available in UK as those were some USA videos I watched, so maybe anyone can link to a stuff what is needed to do this to line & waterproof everything?

2. I want to make a soap box in the wall, how do you go about creating that, just a few small studs to make the box I would have guessed, waterproofed and tiled over I guess? What would be the best way to go to create such soap box and waterproof it after that?

3. How do you go about creating the sloped base for the shower so the water can run in to waste line? Again I saw in some USA videos people already using some ready-made panel which is specially made for this, but the only similar stuff I found here for sale is something way different than what I saw or just insanely expensive, is there any DIY way to create the sloped panel? Or you can just make the level un-even with extra tile adhesive when tiling over everything to create the slope needed?

4. How do you make the Curb on the floor to keep the water at one place+ to attach the glass panel, I suppose the carcass of it could be made from timber, waterproofed and than just tiled over?

Thank you for reading all this & If you got any other tips what would be helpfull would really appreciate them as well

These are the pictures of the stuff that I want to re-create:

 

Thank you Morg, Yes I will be using mosaic tiles for the sloped floor as I don't have much tiling experience other than 1time I have done it

https://www.amazon.co.uk/Everbuild-EVBAQSKIT45-Aqua-Seal-System/dp/B00862ZW34
would this be a good kit for the waterproofing/tanking? Or there's something better for the same price or less?

Also on the walls I currently got the regular plasterboard (under the old tiles which I will be taking off) , would it be worth to take the old plasterboard out and replace with a waterproof one or not worth it? And do you also just paint that waterproofing liquid right over the plasterboard and you are ready to tile over? (and of course sealing the corners/joints with the tape as well before that)

I wish I could just buy the former, however due to the size I need it in, it's going to set me off some £200+ for something I'm sure I could make myself- out of wbp plywood for example which I already have?

Thanks for the explanation on the soap box(niche) as well

 

Sorry but I just don't have the £400+ to waste for some IMPEY plastic former even it makes life much easier if it were more realistic price for what it actually is than yes sure... + I need to make it custom size anyway due to where it's going to be located, so the ready made solutions don't even fit in my case.

I guess you will laugh if I will tell you that my full bathroom rebuild budget is £500 I have bought more or less all materials already and think will be able to do it within £50 range.

6.5m2 bathroom,
that includes:
nice £20/m2 tiles for floor/walls all over ( bought on ebay auction for more or less nothing)
-new top of the range sink , toilet, all very nice mira mixers/heads etc ( again probably around £1200 worth of stuff bought on ebay for £130
- 2 towel radiators
-will need to re-do the ceiling fully
-some new pipes for plumbing
-all the adhesives/grouts/little bits & bobs
-everything for the wetroom build

Probably around £5-£7k build If I had to hire someone/pay the full prices for everything and use the standard already-made solutions, so you can see that even that formed tray is very huge expense for this

 

hahah thanks well..I'm still in a planing process for a week before I get some time off to actualy get on with it, It's not like I don't want to make it perfect and make it to last- I actually do hence doing my research on how to actually do it, I'm aware that by making the base/former from plywood I'm asking for trouble even If I get the slightest detail wrong so still looking for a perfect solution.

I have watched some more YT videos ( again USA ones, as seems like everyone in UK just uses the already made formers or the plastic tubs) and I see they use a mortar bed which they just make themselves making the level as needed instead of a former.

 

ok what do you guys say about building the frame/everything from 18mm wpb plywood as my floor is on wooden joists so I'm not really sure how stable a cement pour/shape would be, but laying all the plywood construction in a fiberglass so it's more stable and totally waterproof?

 

Finally thanks to xmas/newyear got some time to actually start gutting out the old bathroom and building everything.
decided to do it the way I saw it in american videos,however due to pipe layout and overall layout and very thin existing walls had to make some compromises on the design.

-made the base as stable as it can be, under it is some small timber framed base along with 18mm ply just to save on weight,than DPM membrane, small walls made from stacked 2x3 timber and on top cementboard, than poured in semi-wet mortar sloped base armed with some fiberglass strands and than just tanked everything out with the blue membrane with 3-4x coats, did the water test and everything seemed good, no leaks and everything flows as it should.

One question tho, Do you need any special tile adhesive to tile over the blue tanking stuff or any regular flexible adhesive will do?
pics.