Preheat oven to 175° C. Line a 16 or 18 cm springform cake tin with baking paper.
In a large bowl, mix together the dry ingredients: ground almonds, white rice flour, ground rolled oats, teff flour, coconut sugar, cacao powder, and baking powder.
Blend banana with 150 ml rice milk. Add it to the bowl with dry ingredients. Also, add coconut oil and soaked chia seeds. Mix it with a stand or hand mixer for a couple of minutes until combined.
If the batter is too thick, you can add an extra 1 to 2 tablespoons of rice milk.
Pour the batter into the prepared cake tin and smooth the top with a rubber spatula. Bake for approx. 35-40 minutes.
Spread the frosting evenly all over the cake. Decorate with blueberries.