Nepal is an outlier when it comes to flag shape, as it stands out from the norm (rather “two triangles stacked on top of each other”) since according to them: the flag represents Himalaya Mountains & both religions: Hinduism & Buddhism, also the red triangular flag has been a Hindu symbol of victory since the writing of Ramayana and Mahabharata.
That is in contrast to most countries flags as a majority are rectangular in their shape (no matter where from USA, UK, Canada, Japan, Germany, Poland, etc.). I mean, why are most flags rectangle by default rather than being unique on using another shape? I mean, Nepal is the only country where a flag is designed from another shape that differs from a rectangle.



Worth noting that while the rest of the world uses rectangles, it’s not always the same dimensions.
The Swiss flag, for example, is explicitly square. If it’s not square, it’s actually the maritime version specifically.