Place a few ice cubes in a small bowl and fill with water (6 tablespoons worth at least). This will get your water nice and cold. Set aside.
Preheat the oven to 400 degrees Fahrenheit. Line a baking sheet with parchment paper.
Place an additional piece of parchment (about 12x16) on a cutting board or pastry board. Sprinkle some oat flour on top.
In the bowl of a food processor, place oat flour, white rice flour, nutritional yeast, smoked paprika, garlic powder, onion powder, ground turmeric, cane sugar, cayenne pepper, salt, and baking powder. Pulse a few times until the ingredients are incorporated. Take 4 tablespoons of vegan butter and slice small pieces into food processor. Reserve remaining tablespoon of butter. Pulse until mixture becomes a course, clumpy meal. Add 6 tablespoons of cold water and lemon juice. Pulse until mixture comes together.
Turn dough out onto floured parchment paper. Dough will be sticky. Sprinkle a little extra oat flour over dough. Work it in with your hands and dough will become smoother and less sticky.
Press dough down into a rectangle. Cover with another sheet of parchment paper and roll dough into a large rectangle. It should be about 1/16" thick. If it is thicker, you will have softer crackers.
Using a pizza wheel, slice off the uneven ends of rectangle. Score dough into 1-inch squares. Gently transfer squares to prepared baking sheet. Prick the center of each square with chopstick, skewer or tip of knife (if desired) to get classic Cheez-it look.
Melt remaining tablespoon of butter. Brush on tops of squares. Sprinkle with sea salt.
Bake for 12-14 minutes.
Makes about 70 crackers. Store in an airtight container at room temperature for 2-3 days.