Havent gone to Switzerland, but did look into it when I was researching my own.
So it is Medically Assisted, meaning there is a doctor and a nurse to administer whatever medication they used. As far as I can remember it's through IV.
What @Dot & @FlyingFR are referring to is something called a SarcoPod, which is currently under testing/approval in Switzerland. The builder/inventor promised to make the plans available (it's allegedly 3D printer-friendly) but they havent done so yet.
Going back, for facilities that do offer the service of Assisted Dying, I believe you need to submit your medical documents first for review. I believe there are 2 or 3 rounds of review, so it's like a job interview, i guess.
Once you pass these reviews you'd need to go there to have their doctors examine you and confirm the information that's on the documents that you initially submitted for review.
If you're successful, that's when you get to discuss details like date, time, location, what to do with your body after, etc. I believe you're supposed to have a next of kin and or witness with you for your personal effects after.