To make your crust:You will need a food processor for this
Add your rice flour, psyllium husk, salt, tapioca starch, potato starch, and pulse a few times.
You are going to want to cut your butter up into cubes. I like to quarter mine as it make it easier to pulse.
Add your butter to your food processor and pulse a few times. You want the butter to still be visible and be around the size of a pea.
Now, one tablespoon at a time, while you are pulsing your dough, add your water. Once you have added 3 tablespoons, you should see it start to look really crumbly. After 4 tablespoons, it should start to form a ball of dough. If it does not do this with 4 tablespoons, add 1 more and that will do the trick.
Remove your dough from the food processor and cover in plastic wrap (or an eco-friendly alternative) and flatten into a disc. You will want to then cover it completely and place in the fridge for 1 to 2 hours.
Once the dough has properly chilled, you will need two pieces of parchment paper. Place the disc between them and begin to roll out your dough to the necessary size of your tart pan. Place the dough into the tart pan, and if you have excess dough hanging off the side of the tart pan, use your rolling pin to roll over the tart pan, It will force the dough to cut off where you want it to.
Push the dough so that it properly fits into the cracks of you pan. If you have any place that is cracking or has torn, take a piece of the excess dough and just push it on in there.
Place your tart back into the fridge for twenty minutes and in the mean time make your filling.