Preheat the oven to 325º. Line a large baking sheet with parchment paper. Cut a second piece of equally sized parchment paper, and set aside for later use.
In a large bowl, mix oats, pumpkin seeds, sesame seeds, flax seeds, chia seeds, poppy seeds, fennel seeds, caraway seeds, and salt.
In a smaller bowl, whisk together water, olive oil, and maple syrup. Pour the wet mixture over the seed mixture and stir until incorporated. Let this mixture sit for 10 minutes—it will thicken as it absorbs liquid.
After 10 minutes, bring the mixture together into a ball and transfer to the parchment-lined baking sheet. Use damp hands or the bottom of a flat measuring cup to spread the mixture out to ⅛-inch thick.
Bake until golden brown around the edges, 30-35 minutes. Then remove from the oven.
Place the second sheet of parchment paper on a clean, flat surface, and carefully turn the cracker over onto the clean parchment paper, so that the baked side of the cracker is now facing up. If it's still on, remove the top sheet of parchment from the cracker, and transfer the new parchment paper + cracker onto the baking sheet. Bake until firm and golden brown around edges, another 15–20 minutes.
Remove from the oven and allow the cracker to cool on the baking sheet, then break it into pieces of your desired size. Store in an airtight container. Will keep up to a week in a cool, dry place.