A few tips to get started with building

First of all you should replace the default building keybinds, cause building with F1, F2 & F3 is super hard to get fast at building. check out the keybinds of top players here

I'm for example using 'q' for wall, '1' for ramp and '2' for floor, like SypherPK

And now just build, build and build!

If you're just starting out, here is a simple exercise to begin with:

Here is a little harder exercise:

And can you hide a wall and shot immediately? :)

Good luck with your building, and I'll be happy to hear your ways of practicing :)