This recipe made a bit more than I actually needed, but the 3-2-1 math was easier with these measurements, so I just went with it. You would probably be fine starting with 10 or 11 ounces of flour.
Whisk together the flour, salt, sugar and seasonings.
Toss in the butter. Rub in with the tips of your fingers in a rubbing motion until the largest pieces of butter are about the size of marbles.
Very slowly drizzle in the water, a bit at a time, tossing lightly between additions, until the dough is just barely starting to come together.
Squeeze a bit of dough together in your hand. If it all sticks together easily, you're done. If not, keep adding a tiny bit of water at a time, testing the dough each time. Be very conservative with the addition of water as adding too much can activate too much gluten, giving you a crust that fights back when you try to roll it and shrinks up when baked.
Once your dough is ready, plop it on a large sheet of parchment paper and press it down a bit. Cover it with another sheet of parchment, and roll it out in a rough rectangle (if you're using a rectangular pan. If you're making this in a round casserole, roll it into a circle) about 2" larger in diameter than what you need.
Put in the fridge for at least 1/2 hour to hydrate.