How to make 3 blocs to fill the screen?



I have a problem, I would like to make a website which would be divided into 3 sections, the navigator bar on top which would take 5% of screen area, a dynamic area which would take 90% of screen area and a footer which would take 5% of screen area at the bottom. I wish that all of those areas would scale and fill the screen properly regardless of resolution someone is using.

I tried making custom classes for all of these blocs but setting height percentages I mentioned in dimensions tab does not work. Is there possibility to make this within blocs?

thank you