Seal flat roof - liquid plastic

Hello everyone,
we are building a normal rectangular single-family house. However, on the ground floor, a kind of cube is supposed to protrude.
Now there is a flat roof of 75cm on two sides. (approx. 10sqm)
Can you waterproof that yourself with liquid plastic? Sounds easy actually.
Does anyone have experience with that?
Or are there other better options?

Thanks for your answers.
Regards

Let it be done - especially with flat roofs, it is not for someone who has no idea about it...

Our flat roofs are sealed with EPDM foil.

The solution with liquid plastic and the associated fleece looks quite simple. Especially if you are skilled at craftsmanship.

Yes, then just do it that way - so why are you still asking - I have given you a (very good) alternative

I definitely would not save money or experiment with the roof sealing, especially on a flat roof...

Actually, you can't attach anything yourself at all. That is marked as a hazardous material and as an end consumer, you can't get it at all as far as I know. We had it sealed with that. It's very reliable, but it didn’t look easy at all. You have to work quickly, get everything properly and smoothly, and it stinks and is damn hot!

I'm asking because I wanted testimonials. Now I know that it's not that simple after all

Today I'm going to inquire with a roofer.
Thanks for the answers