In Seriously Good Gluten Free Cooking I gave a recipe for pastry. Here is another version. but this time I have added a teaspoon of Xanthum gum an egg and slightly more water, this really makes a big difference to the end result.
If you don't have Xanthum gum you can substitute with 2 tsp Psyllium Husk, this helps to bind well also (both available from health food stores) but you will need to add a little more water as the absorption rate is higher.
This pastry is much easier to roll out, and acts almost like the real thing. You will get a little cracking, but hardly any. You can line flans and tarts now using the normal way of rolling out pastry.
If you are baking blind, line with baking parchment and baking beans, then set the temperature slightly higher, so 180°C Gas 4, to set the egg, then reduce to 160°C Gas 3.
Lift out the baking parchment and beans carefully, covering any cracks, brush thickly with beaten egg and return to the oven to cook and set. Repeat the brushing with egg and baking.
This will give you a great base.