Grease and/or line ~25 x 13 cm (10 x 5 in) loaf tin with oil, then line with baking paper.
Whisk the flour, baking powder, baking soda, cinnamon, nutmeg and sea salt together in a bowl to combine. Set aside.
To make the flax eggs, combine 2 tablespoons of flaxseed meal (ground raw flaxseeds) with 6 tablespoons of water. Mix well and let rest for five minutes to thicken.
Place the sunflower oil and sugar in a stand mixer fitted with a paddle attachment and beat on medium speed until combined. Scrape down the sides and reduce speed to low. Add the flax eggs, mashed bananas, and vanilla extract and mix until well combined. With the mixer on low, add half the flour mixture, followed by the remaining flour mixture until just combined. Remove the bowl from the stand mixer and fold in the chocolate chips. Transfer the batter to the prepared tin.
Optional but not required: arrange banana slices over the batter, sprinkles with seeds or split a banana down the middle vertically, then add on top of the batter. Bake for 60 minutes. Cool for 15 minutes before lifting out of the tin to cool completely before slicing.
Notes
Suppose you decide to split a banana down the middle vertically and add it on top of the batter. In that case, you first bake the loaf for about 10 minutes and then add the banana. This is to prevent the banana from sinking into the banana loaf.