Preheat the oven to 350°F. Prepare two large baking sheets and three sheets of parchment paper.
In a large mixing bowl, combine the almond flour, rice flour, white sesame seeds, black sesame seeds, baking powder, and salt.
Add the olive oil and 7 tablespoons of water. Mix with a sturdy spatula, then use your hands to bring the dough together.
Squeeze a small amount of dough between your fingers. If it falls apart, add the remaining water one teaspoon at a time until the dough holds together. It may still look slightly crumbly.
Divide the dough into two equal portions.
Place the first portion on a sheet of parchment paper and cover it with a second sheet. Roll the dough into a thin rectangle approximately ⅛ inch thick.
Remove the top sheet of parchment. Trim and reshape the uneven edges if desired.
Use a pizza cutter or sharp knife to score the dough into 1½–2-inch squares. Do not separate them. Prick each square once with a fork or wooden skewer, if desired.
Sprinkle the surface lightly with flaky sea salt, if using.
Transfer the rolled dough to a baking sheet together with the bottom sheet of parchment.
Repeat the rolling and cutting process with the second portion of dough.
Bake for 15–22 minutes, until the crackers are dry and golden around the edges. If baking both sheets simultaneously, switch their positions and rotate them halfway through.
Remove the baking sheets from the oven and allow the crackers to cool completely on the pans.
Break the cooled crackers apart along the scored lines.
Store in an airtight container at room temperature for up to one week.