Yeah you can, I've read about people taking cuttings as late as 6 weeks, it just takes longer and gets more difficult to revert back the further in you are. It'll actually work out well if you can keep it alive, reveg/clones from flower can really bush out into monsters
oh yeah, how to..Cut a 4-8" top, throw it right into a bowl of cold water so it floats around, leave it for 5-10 mins. the cutting will absorb water while in there, increasing it's reserves. I'm assuming you're in soil? Fill some cups or something with damp soil, poke a hole in the middle about half the depth of your clones. Take clone out of water, cut about 1/4" off bottom at an angle, strip all ffoliage up to the top set of fan leaves and growth tip, cut those fan leaves in half. scrape stem about halfway up, dip in rooting aid, stick in hole in dirt and pack dirt around it. cover with a dome of some sort, an inverted cup works well, or cut 12oz soda bottle. Take the dome off a couple times a day for a few minutes, give it a shot glass of water if it looks droopy, keep temps above 70..take a couple just in case..