If you want to S1 anything.. from my understand you are asking how to straight up self pollinate them, correct?
If this is the case, you are going to want to use one of the multitude of methods for getting an otherwise female plant to also produce male parts, those being the pollen sacs. When the pollen from such a plant breeds with itself, the seeds created are considered S1's and only contain genetic material from that plant alone and don't have any male genetics to go along with it. This is the reason why 'selfed' plants only produce female offspring.
The method that I think is the most often used to get female plants to produce pollen is by spraying the plant with water containing silver ions. You can either make the silver ion water yourself, or purchase it from any number of places. Usually costs about $50 for 16oz or something like that. Making your own isn't very difficult either, you simply hook up a piece of scrap silver from a necklace or whatever to a voltage source and dangle it in a container of water. The other terminal of the voltage source is also dangled in the water, and I personally also use a piece of scrap silver for this electrode as well. This way it doesn't matter which terminal is positive and which is negative, because both have silver as the electrodes. I'd suggest referencing my explanation from other sources as they probably have better instructions than what I've given, but this is the basic principal.
In theory, you could do this with male plants instead of females, creating male plants which also produce female plant parts (pistils) which could therefore produce seeds. I haven't ever seen it done or heard of anyone trying it, as not many people want to produce seeds that only produce male plants. I suppose if I only had 1 or 2 seeds left of a strain I was trying to save the genetic lineage of, and after growing them out they all turned out to be male, I would likely attempt to produce some all male S1 seeds from them so that I could pollinate something else later on by growing out the male S1's at a time that I knew I would have some females growing which I want to pollinate with that male. It might make for a useful tool in stabilizing a genetic line, because you could reliably have that same genetic male around to pollinate future females with, generation after generation of breeding, also called inbreeding for stability. I'm not sure how long pollen stores for, but I'm assuming that seeds would store more reliably than pollen.
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... can't believe it, think this is the first time I used a GIF in a forum.
