When making Gluten-Free Shortcrust Pastry, it is often necessary to add a small amount of water to hydrate the flour and prevent the pastry from crumbling when you roll it. The amount of water required is dependent on several factors; the type of flour, the humidity and the type of fat used. It is important to add water slowly until the dough just starts to come together. Test by pressing a small amount between your fingertips. If it is still crumbly, gradually add water a teaspoon at a time, just enough so the dough feels damp but is not sticky. If you add too much water and you need to add flour, it will make the pastry tough.