Preheat oven to 350 degrees. Coat a 9-inch springform pan with cooking spray. Line the bottom with parchment paper and spray the paper.
Process whole almonds in a food processor or blender until finely ground (you will have about 1 3/4 cups ground). Beat 4 egg yolks, 1/2 cup honey, vanilla, baking soda, and salt in a large mixing bowl with an electric mixer (or use a paddle attachment on a stand mixer) on medium speed until well combined. Add the ground almonds and beat on low until combined.
Beat 4 egg whites in another large bowl with the electric mixer (use clean beaters on a handheld mixer or the whisk attachment on a stand mixer) on medium speed until very foamy, white and doubled in volume, but not stiff enough to hold peaks, 1 to 2 minutes (depending on the type of mixer). Using a rubber spatula, gently fold the egg whites into the nut mixture until just combined. Scrape the batter into the prepared pan.
Bake the cake until golden brown and a skewer inserted into the center comes out clean, about 28 minutes. Let cool in the pan for 10 minutes. Run a knife around the edge of the pan and gently remove the side ring. Let cool completely.
If desired, remove the cake from the pan bottom by gently sliding a large, wide spatula between the cake and the parchment paper. Carefully transfer the cake to a serving platter. To serve, drizzle the top of the cake with honey and sprinkle with sliced almonds.