About flat bottom dripper
Actually, people start using flat bottom dripper from 1930s (search "Melitta Schnell Filter" if you interested), and they put many sharp ribs on dripper's wall to keep a smooth airflow back to that time. Nowadays we have wave filter so the people focusing more on the bottom support design.
1. The coffee bed in flat bottom dripper is lower than other two types (cone shaped and fan shaped), and I also found that the height of coffee bed in the side is pretty similar to the height in the middle. That makes the extraction more even.
2. The bottom of flat bottom dripper has single or multiple small holes, that means the water that pass through the filter will "get together" in the bottom first, than flow out from the small holes. So your pouring status does not affect the flow rate too much (compare to cone shaped dripper). Makes it very friendly to new users.
3. The unique design of wave filter reduce the contact area of filter and dripper wall, the gaps between filter and dripper helps to keep a smooth airflow.
4. Due to the smaller bottom angle and small holes, the flow rate of flat bottom dripper is slower than cone shaped dripper. Also, it is hard to use your pouring techniques to speed up the flow rate (see point 2). Flat bottom dripper is well known for its stable and balance taste, and base on my experience, it also provide sweeter taste and heavier body due to its longer brew time. In exchange, the performance of aroma and vivid acidity will be weaker. Also, the flavour complexity might perform better when it used with conical burr.
Thanks for reading.