Preheat oven to 350° F and line a large baking sheet with parchment paper. Place oats in a food processor or blender and blend into a flour consistency. Add walnuts and process until broken down into small pieces, approximately 20 seconds.
In a large mixing bowl, whisk together oat flour/walnut mixture, chia seeds, sunflower seeds, and sea salt. In a small bowl, whisk together maple syrup and water.
Add wet ingredients to dry and quickly stir to incorporate. Use a dampened rubber spatula to spread dough into an even layer on baking sheet, approximately 1/4-inch thickness. Try to form as close to rectangular shape as possible.
Bake flatbread for 40 minutes, or until the edges are golden brown and the center is firm to touch. Allow to cool 15 minutes before slicing and serving.
SuperSeed Flatbread will keep tightly sealed on the counter for 2 days, or in the refrigerator for 1 week