Preheat the oven at 325F or 170C.
In a bowl, mix the ground sunflower seeds and salt together until combined.
Add the flax egg, oil and mix until a dough is formed.
Roll the dough between two parchment papers until as thin as possible. Fold the 4 uneven edges of the dough to create a square or rectangular shape. Roll and flatten the edges.
Use a long knife to cut the dough into rectangular shapes. Pizza cutter doesn't work well as it's difficult to cut through the pumpkin seeds. If you cut the dough into rectangular shapes of 1 1/2 x 2 1/2 inches each, you can get 28 pieces. If you cut into squares of 1 1/2 x 1 1/2 inches, you can get 40 pieces. You can easily double the recipe for more servings.
Transfer the cut dough onto a baking tray.
Bake for about 15 to 20 minutes or until browned. Be careful not to brown the crackers too much as they can burn easily due to the thinness. If some of the crackers are not crispy enough, especially those at the center of the baking tray, you can just pop them into the oven and bake a little longer.
Cool completely. The crackers will crisp up once cooled.
Store the crackers in an airtight container for a few weeks at room temperature. They can also be refrigerated and frozen. They taste great straight out of the fridge and freezer.