Add walnuts to food processor and pulse until flour like consistency.
Add almond flour, 1 egg, coconut oil and 2 Tbsp maple syrup into food processor and process until dough starts forming.
Place dough in the middle of your baking pan and spread out with your fingers until the whole pan bottom and sides are evenly covered. Make sure the sides are thick enough to not break when removed from pan. If the dough becomes too sticky either use parchment paper in between fingers and dough or put dough in the freezer for 10 minutes and then start spreading.
Fill a big bowl with lukewarm water and squeeze juice of half a lemon into the water.
Place tart pan with crust in the fridge while slicing apples.
Preheat oven to 350 F (180 °C).
Wash, core and quarter one apple at a time and finely slice it letting the slices fall into a large bowl with lemon water until all apples are sliced. Use a mandolin slicer, a knife will NOT make the trick unless you are a ninja.
Submerge a hand full apple slices 10 seconds in boiling water, remove and then form rose(s) with the slices. Then continue filling pan with apple slices around the rose(s) until full (as described and shown in pictures above).
In a small bowl whisk together evaporated milk, 1 egg, egg yolks, and 1/4 cup maple syrup and slowly and carefully pour custard into wholes between apple slices.
Bake for 35-40 minutes at 350 F (180 °C) until crust and apple tops start browning.
Let cool down to room temperature and then refrigerate for at least 1 hour for custard to solidify to required consistency.
Sprinkle Maple Flakes on top of everything and decorate with flours (optional).