It's not with stackage. You just do pre-setup:

cabal update && cabal install stackage

Building project:

1. clone a project, cd into it

2. stackage sandbox init

3. cabal install --only-dependencies

4. cabal configure && cabal build

If you already used some "lts version", you can put "stackage sandbox init lts-2.4" to second command and it will re-use existing lts-2.4 sandbox without a need to reinstall anything.

That's it. It takes a very long time first time you build with this with some version of lts stackage, and there is some movements towards binary package sets, but I'm not sure on status of that.