Lots of betta breeders set up a breeder tank with the male in the tank free to build his nest and the female restricted in a small area in the tank in view of the male.
After a male is in prime spawning condition they introduce a well conditioned and ripe female. Adding a female that is not ready to spawn will not result in success.
Some breeders use hurricane lamp tops
http://www.cheshirecatantiques.com/images/hurricane2.jpg
to place the conditioned female betta in while the male builds his nest. He is able to court the female without hurting her. When his nest is built and she attempts to follow him to it from inside the lamp she is released. No dumping from one receptacle to another, possibly disturbing the male's nest, just lift the lamp.
I've used this with great success.
It may take a few days from there.
You should provide a hide for the female should she need to retreat from the male and his aggression. For this I used one of those 4x4" green strawberry baskets stuffed with java moss with a small stone on top to keep it from floating. The slots of the baskets were just large enough for the female to get through but would not allow the larger male through.
On my first try it took 3 days to get a spawn. On the third day I was sure I'd have to split up the pair, recondition the fish and try again later but when I came home and grabbed the net to remove the female I found them in a spawning embrace under the male's nest.
Getting them to spawn is testy. It's not always the same every time. Some bettas are easier than others. Ultimately it takes patience.
