I use a 1 deg base and 3 deg side bevel. This is the angle that comes from the factory for all Atomic skis. Even the team race skis have these angles. What a slight base bevel prevents is accidental hooking. With the sidecut of present slalom skis, a slight tip of the ski, and you're turning up the hill. There is nothing written in stone, so go out and test different angles. Most manufacturers do the testing and put certain angles on because that is what they feel will work best with their skis.
AND, tipping the ski 1 deg doesn't take too much time. Having a 0 deg base is not measureable any faster edge to edge than one with 1 deg. The width of the ski determines that.