Whisk together the flour, brown sugar, cinnamon, salt, baking powder, and baking soda in a mixing bowl.
In a large mixing bowl, whisk together milk, oil, and eggs until eggs are beaten.
Add the flour mixture to the egg mixture, stirring to incorporate as you go.
Prepare a 5 to 7 quart slow cooker by lightly greasing, lining with parchment paper, or a slow cooker liner. Pour in batter.
Cover with either a clean dish towel or paper towels before putting on the lid (to prevent condensation from dripping onto the cake) and cook on high for 1 hour.
Prepare the topping by stirring all ingredients together until crumbly. Once the cake's first hour is done, sprinkle on the topping and replace the condensation catcher along with the lid. Continue to cook on high until the cake passes the toothpick test, 30 minutes to 1 hour.
Remove insert from slow cooker and transfer to a cooling rack. Let stand 10 minutes before removing the cake.
Let cool completely before adding the glaze.
Beat all glaze ingredients in a bowl until smooth, then drizzle over cake. If glaze is too firm, add 1/2 to 1 more tsp of almond milk. If too runny, add more powdered sugar until the desired consistency is reached.