Line a 9x9-inch square pan with parchment paper or use a 9x9-inch silicon pan.
In a small bowl, whisk together the ground flaxseed and water. Set aside for 5 minutes to thicken.
Add the almonds and rolled oats to a food processor and process for 15 to 20 seconds, or until a coarse meal forms.
Then, add the flaxseed mixture, almond butter, dates, coconut sugar, and sea salt, and process for 2 to 3 minutes, or until the mixture begins to clump together and hold its form against the wall of the food processor. It should be sticky enough that it holds together well when pressed between your fingers but is able to easily crumble back to its original form. If it isn't sticking together when pressed, add more pitted dates, 1 at a time, and continue to process until it holds together as described.
Scoop the crust mixture into the lined pan and use your hands to press it evenly into the bottom. Then, use the back of a large metal spatula (see above photos) to press and firmly compact into a smooth, even surface.
Freeze for 30 minutes to set.