Preheat the oven to 350° Fahrenheit. Start soaking your cake pan strips (fabric that goes around the pan while wet to keep your cake edges from getting crusty/hard) so that they'll be ready to use. Grease two 9-inch round pans with butter or cooking spray. In a medium bowl, whisk together the flour, almond meal, flaxseed meal, starch, salt, and baking powder, then set aside. In a large bowl, whisk together the eggs, brown sugar, vanilla, and butter until thick and blended. Finely grate the carrots using the smaller holes of a box grater. Using a spatula, stir the grated carrots into the wet ingredients until combined. Dump the dry ingredients into the wet and stir together with the spatula. Before pouring the batter into your pans, make sure you put on your cake pan strips! Then pour half of the batter into each of the two pans. Bake at 350 for 25-30 minutes or until a knife inserted in the center comes out clean. Let cool completely before frosting. If making the 4-tier cake, make the second two cake layers once the first two have cooked, using the same pans (invert the cakes once they've cooled slightly and remove from pan, then let them rest right side up on a plate or tray and wash the pans for a second use).
While the cakes are cooling, make the frosting. Using an electric mixer, beat together your room temperature butter for 4-5 minutes until it's much lighter and fluffy, then add in the cream cheese and continue to beat until lighter and fluffy. Add the powdered sugar one cup at a time, beating in between each addition, then add vanilla and salt and continue to beat until smoother and fully blended.
Once the cakes are completely cool, construct the cake! First, toast your sliced almonds. Pour almonds into a frying pan and heat over medium, stirring frequently, until most of the almonds have gone a touch golden and smell nutty, then remove from heat and pour onto a paper towel to cool. While they're cooling, place the first cake layer on a cake board or serving plate, and use about 3/4 cup of the frosting to coat the top. Place the next layer on top of the frosted first and repeat until all layers are in place and frosted. Then carefully crumb coat the entire cake with frosting (ensure that you have enough frosting leftover for the final coat). Freeze or refrigerate the entire cake for 30 minutes to an hour to set the layers, then remove and apply the final coat of frosting.
Finally, press the toasted almonds into the side of the cake how you like, and add any edible flowers if using. Pipe any leftover buttercream on the top of the cake if desired. Then serve!