In a medium sized bowl, whisk together flour, sugar, 3/4 cup brown sugar, 1 teaspoon cinnamon, salt and baking soda.
In a separate large bowl, whisk the vegetable oil, eggs and milk. Mix the dry ingredients into the wet.
Mix the remaining 1/2 cup brown sugar and 1 teaspoon cinnamon together.
Grease your slow cooker and pour half the batter in. Sprinkle with the brown sugar cinnamon mixture and then pour in the other half of the batter. Cover with a clean dish towel and place the lid on. Cook on high for 2 1/2 hours. Begin checking the cake at 2 hours*, and rotate the ceramic insert halfway through cooking.
In a small bowl, whisk together the glaze ingredients and drizzle on the cake when it is done.
*Note: Different machines take different amounts of time to bake a cake, so it is a good idea to check on it from time to time.