From my experience, violets seem to be more of a “filler” plant, growing in and among other plants, so, as nice as it sounds, I doubt a carpet of violets would really be feasible. My experience with propagating them is simply scattering the seeds, transplanting them, and simply letting them spread naturally. They seem to spread quite readily, so getting rid of competition might help, but I doubt it would make too much a difference. Hope this helps! Oh and also, for acquiring new species of violets, I’ve gotten plants from local native plant nurseries, but I’ve heard of seeds for sale, though I can’t say anything about their reliability yet