Yeah there's really no need to ever sideslip unless the run narrows down REALLY tight and you've got to scrub speed (like in some treed runs or on a chute)...
Otherwise, on a steep wide open piste instead of side slipping to scrub off speed you should be making more dramatic dynamic skidded turns that turn and almost go uphill again.
Alpine boarders basically don't skid at all, yet they control their speed by spending more time going across the hill, than down the fall line.
My suggestion is to get REALLY good at working on your turns on a blue before worrying about ramping up to steeper runs.
so that's a really sharp turn to get yourself almost going back uphill. but that's a good thing for me to practice. thank you. snowboarding for me without goals is tough. now I have many clear cut goals to accomplish.