Pollinate the females very early, when they are just small "tufts" of white pistils, let grow for 4-5 weeks and bingo!
Remove the seeds from flowers, either when wet or dry.
I like to use a wooden bowl for seed drying, about three weeks, then store the seeds in an airtight container in the refridgerator until planting time.
Even just half a dozen branches pollinated will give you 100-400 seeds.
Just remember to use pollen from a pure male plant, pollen from a hermaphrodite will produce hermaphrodite dominant genetics in the seeds.
The female plants growing the seeds will need good hydration to produce decent seeds, otherwise, making/growing seeds is super simple with no real tricks or difficulties involved.
Obviously you will have to grow a male plant first and preferably in another location, unless you want your entire crop of females fully seeded! (Reversing females to make feminized pollen is technical and a bit difficult, much easier to do it the natural way)
Pollen can be collected and stored in a dry, dark and cool location, (but not in the fridge!) for later use, for up to 3-6 months with virtually no loss of pollinating power. I use a small paint brush to selectively apply pollen to the chosen female flowers, usually on the lowest branches, that way you can harvest the top of the plant and leave the lower section go a bit longer if the seeds still require extra maturation time. Pollinate the female flowers when it is windless. Fertilization only takes 30 minutes or less and after 45 minutes I spritz the pollinated flowers with plain water to neutralize any stray pollen and prevent unwanted windborne random pollination in flowers you want to be seedless further up the plant.
If you only have a small amount of pollen, it can be "diluted" with flour at a ratio of up to 50:1 and you will still achieve 100% pollination, as pollen is extremely fine and only one grain of pollen needs to land on a white pistil for fertilization to occur.
Naturally, all seeded flowers are sacrificial, so can be thought of as a stepping stone to a bigger picture.
Creating your own hybrids is an extremely rewarding and a fascinating hobby. I have created many strains, one in particular which contain genetics from Gorilla Glue, Girl Scout Cookies, White Widow, G-13, Black Domina, Jack Herer, San Fernando Lemon Kush and Cream Caramel; along with Nepalese, Jamaican, Thai and African land-race genetics too, really is quite spectacular, even if I do say so myself! This multi, multi hybrid has been a few years in the making and has become a real surprise pakage. I am almost satisfied with it so far, but I may introduce a bit of early finishing pure Sativa for a bit more zing!
Once you start breeding, you won't be able to stop, as there is always "what about if I introduce a bit of ...... " or "what if I cross this with that, or that, or that"
Good luck with your own projects, I guarantee you will love it!
Hope this helps or inspires you.
Cheers, Organoman.