Preheat oven to 350F. Line 2 large baking sheets with parchment paper.
In a medium bowl, mix the almond butter, sugar, egg, vanilla, and water until thoroughly combined.
Add the cocoa powder, flaxseed, and baking soda, and whisk until the cocoa powder is fully incorporated.
Transfer the dough to an airtight container and refrigerate for 1 hour or up to 5 days. Use a cookie scoop or large tablespoon to scoop the dough into rounded tablespoonfuls onto the baking sheet.
Bake for 10 minutes, until the edges are set. The middles will be slightly soft. Allow the cookies to rest for 3 minutes, before serving.