How do I make a siyum without a minyan?
There is no need for a Minyan.
You should learn (even beforehand) and finish on Erev Pesach one of the following (in order of preference):
- Masechta of Gemara (Maseches Tomid is short)
- Masechta of Mishnayus (preferably with a Pirush such as Bartenura etc.).
If that is not possible you may rely on hearing a live Siyum via telephone etc.