Preheat oven to 350 degrees F (176 C) and either line an 8x8-inch baking dish with parchment paper, or grease a standard pie dish. Set aside.
Add oats, almonds, sea salt (optional), and sugar to a high speed blender and mix/pulse on high until a fine meal is achieved.
Remove lid and add melted coconut oil (1/4 cup as original recipe is written // adjust if altering batch size), adding more if it's too dry. Pulse/mix on low until a loose dough is formed, scraping down sides as needed. You should be able to squeeze the mixture between two fingers and form a dough instead of it crumbling. If too dry, add a bit more melted coconut oil.
Transfer mixture to pie pan or baking dish and spread evenly to distribute. Then place parchment paper on top and use a flat-bottomed object, such as a drinking glass, to press down firmly until it’s evenly distributed and well packed on the bottom and up the sides.
Bake for 15 minutes, then increase heat to 375 F (190 C) and bake for 5-10 minutes more, or until the edges are golden brown and there is some browning on the surface. Remove from oven and set aside to cool.
In the meantime, prepare pudding by adding cornstarch, sugar, and salt (optional) to a small saucepan and whisk in almond milk to avoid clumps (see photo).
Place over medium heat and cook until bubbling, whisking frequently. Then reduce heat to low and continue cooking for 4-6 more minutes, using a rubber spatula to scrape the sides and bottom almost constantly.
Once it appears "jiggly" and a visible ribbon forms when you drizzle some over the top with your spatula, remove from heat, whisk in vanilla, and let cool 10 minutes. Then transfer to a glass or ceramic bowl and cover with plastic wrap, making sure the plastic wrap is touching the surface or it will form a film on top. Refrigerate until cooled and set - about 2-3 hours.
In the meantime, place a medium-large glass mixing bowl in the freezer for your coconut whipped cream. Remove coconut cream can from fridge, being careful not to shake or turn it and remove top. Gently scoop out the top hardened "cream" into the chilled bowl, leaving any liquid watery portion behind. You can use this for smoothies or in baking, if you wish. Otherwise discard it.
Use a handheld mixer to whip the coconut cream until it begins to look like whipped cream (see photo) - about 1 minute. Then add vanilla extract and lesser amount of powdered sugar (3 Tbsp as original recipe is written // adjust if altering batch size). Beat again until light and airy - about 2-3 minutes. Set in refrigerator (uncovered) to chill (for at least 30 minutes or up to overnight).
Once the pudding is completely cooled, is jiggly and set, add to the coconut whipped cream and stir lightly until just combined. Set in refrigerator (no need to chill longer, but it can chill for up to 2 days before adding to the crust).
Add sliced banana to the bottom of the baked crust, then top with custard-coconut whip mixture. Smooth the top with a spoon, then cover with plastic wrap and set in the refrigerator for at least 4 hours, preferably overnight, to chill/set.
To serve, top with additional coconut whipped cream (optional) and more sliced bananas (I used two // amount as original recipe is written // adjust if altering batch size), slice and enjoy! Store leftovers gently covered in the refrigerator up to 3 days, though best within the first 48 hours.
*I would not recommend subbing the cornstarch for arrowroot starch. It makes the pudding sticky and unusable. I don't have any other recommendations for starches, and think cornstarch is best! *When you add coconut sugar in the pudding, it makes it taste like butterscotch (!!!). A separate, perfected recipe for this is coming soon. But to keep this pudding more like a traditional vanilla custard, I recommend using organic cane sugar! *If you aren't serving this within 24 hours, wait to add the bananas on top as they get brown quickly. *Nutrition information is a rough estimate calculated without additional coconut whipped cream on top. It was calculated with two total bananas per 8 slices.