Preheat oven to 350 degrees F.
Combine ground flax seed and water in a small bowl. Set aside.
To make crust, pulse walnuts, oats, and dates in the bowl of a food processor until everything comes together. You'll know it's mixed completely when it sticks together if you press on it.
Press crust mixture evenly into the bottom and sides a 9-inch pie plan. Set aside.
In a large bowl, whisk together the almond milk, flax+water mixture, pumpkin, stevia (or sugar), and pumpkin pie spice. Mix together well.
Pour the mixture into the prepared pie crust and bake for 45-60 minutes, until the center is mostly firm.
Let cool completely to room temperature, at least 4 hours, preferably overnight. This will allow the pie to completely firm up.