Stir together in a large bowl flour, flax-chia blend, baking powder, salt, onion and garlic powders (and chipotle powder, if using). Cut in butter with a pastry cutter until mixture resembles coarse crumbs. Stir in 3/4 cup water and olive oil with a fork until dough sticks together and pulls easily off the sides of the bowl. Add more water, if needed, a bit at a time. Divide dough in two. Working with one piece of dough at a time, place on a floured surface and roll out as thin as possible. Cut into squares and place on prepared baking sheet. Repeat with remaining dough.
Bake in preheated oven until crackers are crispy and golden, approximately 8 minutes. Transfer to a wire rack to cool completely.
Notes: Freeze the butter and grate into flour mixture to get desired coarse crumbs. Roll dough out to desired thinness between two large pieces of plastic wrap; remove top layer of wrap, cut cracker squares and use bottom layer of plastic wrap to transfer cracker squares by flipping them onto prepared baking sheets. Remove remaining plastic wrap before baking.