Your chair has to match a specific target group or serve a specific purpose.
e.g. design a chair for a celebrity, matching his/her image. Or design a chair for your granddad having this peculiar hobby...
Mind you: it has to be a flatpack construction.
Make your model scale 1:5 out of corrugated cardboard.
(or scale 1:1 if you like a challenge) It is ergonomically correct, naturally.