If you don't have gluten free pastry on hand, you can always make a lovely rice crust, which is delicious and wholesome too. (glutenfreedelightfullydelicious.com)
The high heat of the grill helps form a delicious rice crust with a smoky flavor. (baconandsouffle.com)
No color or crunch, just a hard rice crust at the bottom of the pan... Do you think the celery made it too wet? (smittenkitchen.com)