After mixing the egg and potato mixture around a little bit, I began adding flour. I started with a half a cup and mixed that in and then added in more bit by bit until everything came together nicely into a dough.
After that, I dumped the contents of the bowl onto my counter (making a big mess) and worked it around a bit until I got a ball of slightly sticky dough. The important thing here is to use as little flour as possible to get everything to hold together. There's no set amount because relative humidity in the air, the potato, and the amount of starch in the potato all play a factor.
What you should end up with is a ball of dough that stays together and is slightly sticky. If it's not sticky, you added too much flour.
