Prepare your work surface by placing a large piece of parchment paper directly on the countertop, making sure to get it as smooth as possible, then brush the surface of the paper with oil. Prepare another piece of parchment paper approximately the same size or a bit larger than your baking sheet (the parchment is for placing on top of the dough while rolling out, and then for baking the crackers on) by brushing one side of it with oil.
Preheat oven to 350°F.
Blend all dry ingredients together in a large bowl, then add water and oil. Mix well with a wooden spoon, then tip out onto the prepared piece of parchment paper on the counter. The dough may seem a bit dry and stiff at first, but once you knead it for thirty seconds or so, it will start to soften up a bit. The dough needs to be stiff so that it can be rolled out smoothly - if it's too soft, it will just stick to the paper and not really hold it's shape properly.
Once the dough has been kneaded, press it out into a rectangular shape on the parchment paper, and place your piece of oiled parchment paper on top (oiled side facing the dough). Start rolling out and try to get it quite thin, approximately 1/16th to 1/8th of an inch; this will make nice crispy crackers. If the dough starts to spread out further than the size of the parchment paper, just trim those pieces off and save them; you may have to bake the crackers in two batches if they won't all fit on the baking sheet at once. You can re-roll this dough as many times as necessary without making the crackers tough.
When the dough is rolled out thinly and evenly, flip the whole parchment/dough sandwich over, and peel off the bottom piece of parchment paper. Slice the dough into cracker shapes with an oiled pizza cutter, sharp knife, or cookie cutter, then transfer the parchment paper to your baking sheet and into the oven.
Bake for about 15 to 20 minutes, until crackers are starting to brown and have become nice and crisp. When they are finished baking, transfer them from the parchment paper to a cooling rack. Once they have cooled, break them apart and store them in a sealed container at room temperature.