Heat oven to 375°F. Line a baking sheet with parchment paper.
In a large bowl, mix oats, pumpkin seeds, sunflower seeds, sesame seeds, chia seeds, poppy sees, nutritional yeast and salt.
In a medium bowl, stir together olive oil, maple syrup and ¾ cup room temperature water.
Pour liquid mixture over seeds and oats and stir to combine. Let stand for 10 minutes until oats soften and mixture thickens.
Transfer mixture to parchment paper lined sheet. Place another sheet of parchment paper on top and gently smooth out, using your hands or a rolling pin to flatten to ⅛ inch thick. Remove top sheet of paper.
Bake for 15 - 20 minutes. Remove from oven. To flip over to the other side without breaking, place the second piece of parchment paper on the cracker. Invert an additional baking sheet on top, then grasping both sheets (using stove mitts) flip over. Remove the (hot) baking sheet, gently peel off the parchment paper and return to the oven to bake for an additional 15 minutes, or until lightly browned at the edges.
Remove from oven, let cool on pan. When completely cool, cut or break into pieces. Store in air-tight container.