Question about stunting my plant

I have very limited space in my box. How do I stunt my plants. Should I top them early? Lets say I wanted them to be only 2 foot. Do I top them early? Try to flower them early?

Your advice ..please

flower them ASAP

Just buy Dwarf seeds mate

http://www.cannabis-seeds-bank.co.uk/index.php?searchStr=dwarf&specify=any&act=viewCat&Submit.x=0&Submit.y=0&Submit=Go

Here is Pictures of someone growing dwarf seeds:
https://www.rollitup.org/grow-journals/467615-cfl-kc36-royal-dwarf-13.html

LST (light stress training).