Place all ingredients into a mixer/blender and purée until smooth and sticky. Use fingers to press the mixture into the tin, creating a raised edge all around. Immediately place the tin into the freezer.
Bring the almond milk, vanilla, cinnamon, cardamom and salt to the boil. Add the Maizena express and agar agar, whisk and return to the boil. Simmer for around 2 minutes whilst stirring constantly, then stir in the maple syrup and allow to cool slightly. Pour the mixture onto the base and allow to cool in the fridge. Cook the apple slices in water with a little lemon juice for 5-10 minutes until soft, then roll the slices up and place them onto the cake.
Dust the cake with icing sugar before serving.