To make pie dough in the food processor add the flour and salt to the processor and pulse for a few seconds to mix. Then add in the cubed butter and pulse four to five times until the butter has broken up into smaller bits and has dispersed through the flour. Remember the "pea-sized" rule! Continue to pulse in short bursts as you add the ice cold water through the feed tube and stop as soon as the dough comes together. However, if you are new to pie baking, you should avoid using the food processor until you have a good sense of what the size of the butter particles in the flour should be, how pie dough should feel and look as you mix water into it, etc. That's because a food processor mixes fast and warms up fast and unless you know what you are doing it could end up melting the butter quickly and develop gluten in the flour--both undesirable outcomes.