Line a baking sheet with a baking mat or parchment paper. Set aside.
Put a cup of water with ice cubes in the freezer.
Add flour, sugar, and salt to the food processor. Pulse.
Add solid butter and pulse until there are pea-sized pieces of butter.
Add ice water 1 Tablespoon at a time until dough-like consistency (it took me about 5 Tablespoons).
Using a rubber spatula, pour the dough on a sheet of plastic wrap. Wrap the dough into a ball and place in the fridge for 30 minutes to rest.
Remove dough from fridge and place on a lightly floured countertop. Using a rolling pin, roll out into 1/8" thick, 8-10" diameter circle. Transfer to lined baking sheet.
In a medium mixing bowl, add all the ingredients for the filling and mix well. Set aside.
Assemble and Bake:
Preheat oven to 400 degrees Fahrenheit.
Spoon 1-2 Tablespoons of almond meal onto rolled out dough, leaving 1 inch clearance around the circumference to fold galette.
Place rhubarb filling in the center. Leave a 1/2-3/4 inch border around the pie dough.
Gently fold edges of pie dough towards the center around all the sides. Sprinkle turbinado sugar on top of the dough.
Bake for 25 minutes. Remove from the oven and sprinkle crust with almond slices. Place back in the oven and bake for 15 more minutes.
Let cool for at least 10-15 minutes before cutting. Serve warm with ice cream.
Let the galette cool completely and then transfer to an airtight container or wrap in plastic wrap. Keep in the fridge for 3-4 days.To reheat, place on a baking sheet and bake in a 350 degree oven for about 10 minutes.Rhubarb does not do well when frozen and then defrosted and baked again, so don't freeze this one.