Prepare pie crust according to your recipe (you can find my recipe in the notes below). Place the bottom crust in a 9 inch glass pie plate. Keep this in the fridge while preparing the rest of the recipe.
Preheat the oven to 220 C (425 F). In a small saucepan, melt the butter. Add the flour and mix until a paste forms. Add the water, white sugar, and brown sugar, and bring to a boil. Reduce heat and let mixture simmer for a few minutes.
Toss the sliced apples with cinnamon and nutmeg until evenly coated.
Fill the prepared pie pan with the sliced apples so that there is a mound of apples covering the crust. Pour most of the syrup over the apples evenly, reserving a small amount of syrup to pour over the top crust.
Place the top crust over the apples whichever way you like. I prefer doing lattice style strips. Pour the remaining syrup over the top crust to glaze it, trying to avoid it running off the crust and out of the pie pan.
Bake for 15 minutes, then reduce the temperature of the oven to 180 (350) and bake for another 45 minutes. When the pie is ready, the crust will be golden brown and apples will be bubbling. Allow the pie to rest for at least 30 minutes before serving so that the filling has time to thicken up (we ate it immediately and it was still delicious, but leftovers were even better).