you should def take something else, it's one of the shittiest methods out there and it's super easy to give up mid way or do it wrong, plus you can easily get parts of your body paralyzed or have at least some type of permanent nerve damage if your survive.
but i mean if you really really want to go like that, this is how to do it the right way (there's only really one way to do it that's actually works):
so first off you're going to have to cut arteries open. that means cutting real deep like beyond skin level, in either your arms, or upper thighs. you're going to have to also do it in a very spec way to hit the artery and not cause horrible nerve & tendon damage. for arms that means doing 3 cuts, one straight accross on your wrists, an other one accross that cut but not straight accross (like this / but more slanted) & the last and most important one, the straight accross your forearm cut (start straight accross the first cut and cut as long as you can. try aiming to cut your whole forearm). you're also going to probs have to go again a few times in the cuts until you get deep enough.
for thighs i don't really know how to do it exactly, except that you'd have to cut in your inner thigh to get the artery. tbh stick with arms, it's easier cos there's less fat on them and the arteries aren't as deep.
so to be able to do that anyways, cos i mean it's not really realistic to just get a cutter slider and just try to do that like that. you're going to need to numb the area first. to do that, get a bucket or two of ice cold water with lots of ice in it if you want to cut your arms or ice wrapped in something not super thick for thighs. you're going to want to let them numb out for 40 min or so or whenever they're totally numb. after that you're going to want to empty the buckets and put water in them or fill the sink with water and close the drain (or if you want try starting a bath before you numb the area). so when you're done cutting, you can bleed out faster and not clot. then try to do the cuts as fast as you can, so you have less time to hesitate. then just let yourself bleed out in the water. shouldn't take long before you pass out
edit: also you should die in like 20 min or so, and pass out in just a few min. it's a pretty quick method