Hello and welcome to LQ.
You can hardly make a minimal installation including KDE, as you'll need most packages included in Slackware.
If you don't need an installed package, well... Just don't use it. Having it installed won't hurt at all.
Among the packages series you could skip:
D and K if you don't want to compile software. but sooner or later you'll need to
E if you don't use emacs
F if you don't want FAQs and HowTos
T if you don't use Tetex and friends
TCL if you dont' use Tcl/Tk
XFCE if you don't want it
Y if you don't want some games
But again, you won't win anything in omitting these, but a few MB in your hard disk.
Oh, and you can use an installer speaking Portuguese (Brazil) if you want, see http://slint.fr/pt_BR/installer.html