From seed a quick flower (under 30 day's) is touchy it will work but the plant is not mature enough to produce as high THC % in the trichomes as if it were older when you started to flower. It takes on average 30 day's for all the antioxidants to form and mature.

Clones are a different story all to together, a clone inherits the age of the mother so once they have roots you can flower them.