The deeper into flower you get the harder it is to root cuttings. But the easiest way to root cuttings is to cut the bottom at a 45º angle, strip all leaves except the top 3 or 4, and then put them in a full cup of perlite with an inch of water at the bottom. Sink the stems into the perlite so the bottom of the stem sits just above the water level. I do 3 or 4 to a cup.
I use cups with a hole an inch up to make sure I know where the water level actually is!
Then just keep them warm and lit (not too bright...shaded corner of the plant closet will work) and wait a couple of weeks. Then check back in and I'll tell you how to float the stems out.
The faster but more complicated way I clone is
here.
I thin a week before flip and then after stretch is over (3 weeks or so on mine but on a stretchy sativa it will be longer).
Pre-flip, all the weak lowers go along with the leaves, and post stretch the leaves stay and the short branches go. Don't try for #nolarf on a true sativa because you'll be losing a lot of your harvest that way.