Preheat the oven to 400°F (200°C). Prepare two sheets of parchment paper or one silicone baking mat along with an additional parchment sheet, ensuring they fit a baking tray approximately 10x15 inches (25x38 cm).

In a large mixing bowl, combine the rye flour, salt, and baking powder. Stir until evenly blended. Add the rolled oats, pumpkin seeds, sesame seeds, and flaxseeds, mixing thoroughly so the seeds are well distributed throughout the flour mixture.

Pour in the olive oil and water. Stir gently just until the dough comes together into a cohesive mass. The dough should be slightly stiff yet still pliable and easy to spread; add a touch more water if it feels too dry.

Transfer the dough onto the silicone mat or the first piece of parchment paper. Gently press it down to flatten slightly. Place the second piece of parchment paper over the top. Using a rolling pin, roll the dough evenly until it is spread close to the edges of the parchment. If the dough extends too far, trim the excess and patch any thinner areas, covering again with parchment and rolling lightly to seal.

Carefully remove the top parchment layer. Move the mat or bottom parchment with the rolled dough onto the baking tray. Using a sharp knife or pizza cutter, lightly score the surface into squares or rectangles of your desired cracker size — about 24 crackers can be made from this batch.

Place the tray in the preheated oven and bake for approximately 20 minutes, or until the surface feels dry and firm, and the edges start to take on a deeper golden hue.

Allow the crispbread to cool for a few minutes on the tray before cutting along the scored lines to separate into individual crackers. Cool completely before serving or storing.