Yep it’s super easy to do. Usually a stiff older branch atleast 1/4” thick, but not woody yet. Do a cleft graft, it works the best I have found. Leave it in the shade for a week after, or dial back your lights like 75%. Wrap the stem with a small bit (2”x1” peice, think tape) of Saran Wrap, painters tape, or grafting parafilm so the graft doesn’t dry. A drop of Elmer’s wood glue over the union helps too. The scion (cut being grafted) should only be 2-3 nodes long, snip all the leaves, leave the leaf buds by leaving 1/4 stump on the petioles. You don’t want to cut them down to the stem. Easy peasy. That said I am not a fan. I would rather turn and burn. The growth doesn’t take off for 2-4 weeks. Pest too. Here was from a tread I replied to last year:
*What a good thread and question to ponder @Squatch. Here are my thoughts. Avid fruit tree grafter here. I do probably 50-100 bench grafts to rootstock and another 50-100 cleft grafts every year. I sell fruit trees at the PTA plant sale every year.
The main advantage with trees is that it takes 4-5 years to pheno hunt. If you find your seed sprouted tree is crab apples you can take a known cultivar and use the root stock of the crab apple to grow a new top. Without loosing those 4-5 years. Or take an old overgrown tree and turn it into a Frankenstein tree of many fruits. Think urban fruit tree revitalization. With fruit there are early, mid, and late ripening varieties that can chronologically make the tree more spread out and productive.
Also, like mentioned above by @Spiney_norman, grafting trees is often used for proven pest resistant root stock. Or rootstock proven to dwarf an otherwise larger stretch monster tree. This is all relevant for fruit due to the long life expectancy of trees compared to annuals.
Cannabis will graft as easy as the tomatoes. Easier than fruit trees even. This is all counter productive in cannabis. Different flower times due to different top work would make growing that plant more difficult as nutritional needs change on a fast growing annual. Think putting a fast indica and a 16week Sativa on the same rootstock. Who do you cater too? As in there is varying ripening times on the finishing flowers. Also, the time waiting for the graft to callous over (heal) would be as long to veg a seedling and flip it to flower. One could pheno hunt and flip the seeds to flower before the graft heals. Time is working against you on the graft. Then there is introduction of viruses. If you put ten top works on one mother root stock you have to insure that those 10 individual tops aren’t sick. If one grows 10 seeds there is a good chance 1 plant will be sickly. It can be removed or given extra love. If all are on one rootstock all the eggs are in one basket so to speak it would spread to the other tops. It’s an IPM nightmare.
The only reason to do it besides pure enjoyment (trust me I get that aspect) would be in an anal retentive plant count (like some of the earliest medical markets 20 years ago) where one can only have a few plant counts. Back when genetics were harder to trade or come upon for the average self grower.
If you want to become a grafter I would humbly reccomend trying it on a couple of fruit trees. Apples and pears are the easiest. Persimmons and peaches are the toughest. Cherries are in the middle. Cannabis and tomatoes are easy to graft. Most tomato growers I know graft because they start indeterminate style (everfruiting vining) cultivars early indoors to grow big roots. Those varieties grow much bigger and tend to be smaller fruits like Roma and cherry tomatoes. Then they top work to the rootstock a determinate variety like beefsteaks or pounder (Slicing tomatoes) that tend to be smaller plants and roots. Determinate ones are more like auto flowers. They fruit a bit and die. No vining or stretch. Tomato grafting gives you the best of both and is quite popular on the vegetable growing/fruit forums for that reason.*