I used to sell seeds from my plants, and the packets I produced for them, based on the instructions I had successfully used, were
"Sow seed from Dec – Feb. sowing thinly onto the surface of moist, peat-based compost in trays or plastic pots. Cover the seed with fine grit or a little sieved compost.
Keep in a light, well-ventilated place such as a cool greenhouse or frame. Never allow surface to dry out, especially after germination has taken place. Germination takes two weeks to several months;
Damping-off can be a problem. The chances of this occurring should be minimized by applying very dilute fungicide when the first seedlings emerge. Prick out seedlings at the two or three leaf-stage. handling the leaves only. Transfer gently to the same light compost, avoiding compaction.
Keep in a shady place until growth has resumed. Keep the plants growing actively, and repot before the pots become root-bound. It is important not to let the plants suffer a check in growth. Transfer to larger pots or into the garden when large enough."
I never had any plants self-seed successfully. Collected seed needs to be stored in the fridge, in a paper envelope then a plastic container.